Problem: While Grisha was celebrating New Year with Ded Moroz, Misha gifted Sasha a small rectangular pond of size n × m, divided into cells of size 1 × 1, inhabited by tiny evil fishes (no more than one fish per cell, otherwise they'll strife!).

The gift bundle also includes a square scoop of size r × r, designed for fishing. If the lower-left corner of the scoop-net is located at cell (x, y), all fishes inside the square (x, y)...(x + r - 1, y + r - 1) get caught. Note that the scoop-net should lie completely inside the pond when used.

Unfortunately, Sasha is not that skilled in fishing and hence throws the scoop randomly. In order to not frustrate Sasha, Misha decided to release k fishes into the empty pond in such a way that the expected value of the number of caught fishes is as high as possible. Help Misha! In other words, put k fishes in the pond into distinct cells in such a way that when the scoop-net is placed into a random position among (n - r + 1)·(m - r + 1) possible positions, the average number of caught fishes is as high as possible.

Input

The only line contains four integers n, m, r, k (1 ≤ n, m ≤ 105, 1 ≤ r ≤ min(n, m), 1 ≤ k ≤ min(n·m, 105)).

Output

Print a single number — the maximum possible expected number of caught fishes.

You answer is considered correct, is its absolute or relative error does not exceed 10 - 9. Namely, let your answer be a, and the jury's answer be b. Your answer is considered correct, if <image>.

Examples

Input

3 3 2 3


Output

2.0000000000


Input

12 17 9 40


Output

32.8333333333

Note

In the first example you can put the fishes in cells (2, 1), (2, 2), (2, 3). In this case, for any of four possible positions of the scoop-net (highlighted with light green), the number of fishes inside is equal to two, and so is the expected value.

<image>

Solution (in JAVA):

Solution:
import java.io.*;
import java.math.BigInteger;
import java.util.*;
import java.util.function.BiConsumer;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Supplier;
import java.util.stream.Stream;

public class D_456
{
	public static final long[] POWER2 = generatePOWER2();
	public static final IteratorBuffer<Long> ITERATOR_BUFFER_PRIME = new IteratorBuffer<>(streamPrime(1000000).iterator());
	private static BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
	private static StringTokenizer stringTokenizer = null;
	private static PrintWriter out = new PrintWriter(new BufferedOutputStream(System.out));

	static class Array<Type> implements Iterable<Type>
	{
		private final Object[] array;

		public Array(int size)
		{
			this.array = new Object[size];
		}

		public Array(int size, Type element)
		{
			this(size);
			Arrays.fill(this.array, element);
		}

		public Array(Array<Type> array, Type element)
		{
			this(array.size() + 1);
			for (int index = 0; index < array.size(); index++)
			{
				set(index, array.get(index));
			}
			set(size() - 1, element);
		}

		public Array(List<Type> list)
		{
			this(list.size());
			int index = 0;
			for (Type element : list)
			{
				set(index, element);
				index += 1;
			}
		}

		public Type get(int index)
		{
			return (Type) this.array[index];
		}

		@Override
		public Iterator<Type> iterator()
		{
			return new Iterator<Type>()
			{
				int index = 0;

				@Override
				public boolean hasNext()
				{
					return this.index < size();
				}

				@Override
				public Type next()
				{
					Type result = Array.this.get(index);
					index += 1;
					return result;
				}
			};
		}

		public Array set(int index, Type value)
		{
			this.array[index] = value;
			return this;
		}

		public int size()
		{
			return this.array.length;
		}

		public List<Type> toList()
		{
			List<Type> result = new ArrayList<>();
			for (Type element : this)
			{
				result.add(element);
			}
			return result;
		}

		@Override
		public String toString()
		{
			return "[" + D_456.toString(this, ", ") + "]";
		}
	}

	static class BIT
	{
		private static int lastBit(int index)
		{
			return index & -index;
		}

		private final long[] tree;

		public BIT(int size)
		{
			this.tree = new long[size];
		}

		public void add(int index, long delta)
		{
			index += 1;
			while (index <= this.tree.length)
			{
				tree[index - 1] += delta;
				index += lastBit(index);
			}
		}

		public long prefix(int end)
		{
			long result = 0;
			while (end > 0)
			{
				result += this.tree[end - 1];
				end -= lastBit(end);
			}
			return result;
		}

		public int size()
		{
			return this.tree.length;
		}

		public long sum(int start, int end)
		{
			return prefix(end) - prefix(start);
		}
	}

	static abstract class Edge<TypeVertex extends Vertex<TypeVertex, TypeEdge>, TypeEdge extends Edge<TypeVertex, TypeEdge>>
	{
		public final TypeVertex vertex0;
		public final TypeVertex vertex1;
		public final boolean bidirectional;

		public Edge(TypeVertex vertex0, TypeVertex vertex1, boolean bidirectional)
		{
			this.vertex0 = vertex0;
			this.vertex1 = vertex1;
			this.bidirectional = bidirectional;
			this.vertex0.edges.add(getThis());
			if (this.bidirectional)
			{
				this.vertex1.edges.add(getThis());
			}
		}

		public abstract TypeEdge getThis();

		public TypeVertex other(Vertex<TypeVertex, TypeEdge> vertex)
		{
			TypeVertex result;
			if (vertex0 == vertex)
			{
				result = vertex1;
			}
			else
			{
				result = vertex0;
			}
			return result;
		}

		public void remove()
		{
			this.vertex0.edges.remove(getThis());
			if (this.bidirectional)
			{
				this.vertex1.edges.remove(getThis());
			}
		}

		@Override
		public String toString()
		{
			return this.vertex0 + "->" + this.vertex1;
		}
	}

	public static class EdgeDefault<TypeVertex extends Vertex<TypeVertex, EdgeDefault<TypeVertex>>> extends Edge<TypeVertex, EdgeDefault<TypeVertex>>
	{
		public EdgeDefault(TypeVertex vertex0, TypeVertex vertex1, boolean bidirectional)
		{
			super(vertex0, vertex1, bidirectional);
		}

		@Override
		public EdgeDefault<TypeVertex> getThis()
		{
			return this;
		}
	}

	public static class EdgeDefaultDefault extends Edge<VertexDefaultDefault, EdgeDefaultDefault>
	{
		public EdgeDefaultDefault(VertexDefaultDefault vertex0, VertexDefaultDefault vertex1, boolean bidirectional)
		{
			super(vertex0, vertex1, bidirectional);
		}

		@Override
		public EdgeDefaultDefault getThis()
		{
			return this;
		}
	}

	public static class FIFO<Type>
	{
		public SingleLinkedList<Type> start;
		public SingleLinkedList<Type> end;

		public FIFO()
		{
			this.start = null;
			this.end = null;
		}

		public boolean isEmpty()
		{
			return this.start == null;
		}

		public Type peek()
		{
			return this.start.element;
		}

		public Type pop()
		{
			Type result = this.start.element;
			this.start = this.start.next;
			return result;
		}

		public void push(Type element)
		{
			SingleLinkedList<Type> list = new SingleLinkedList<>(element, null);
			if (this.start == null)
			{
				this.start = list;
				this.end = list;
			}
			else
			{
				this.end.next = list;
				this.end = list;
			}
		}
	}

	static class Fraction implements Comparable<Fraction>
	{
		public static final Fraction ZERO = new Fraction(0, 1);

		public static Fraction fraction(long whole)
		{
			return fraction(whole, 1);
		}

		public static Fraction fraction(long numerator, long denominator)
		{
			Fraction result;
			if (denominator == 0)
			{
				throw new ArithmeticException();
			}
			if (numerator == 0)
			{
				result = Fraction.ZERO;
			}
			else
			{
				int sign;
				if (numerator < 0 ^ denominator < 0)
				{
					sign = -1;
					numerator = Math.abs(numerator);
					denominator = Math.abs(denominator);
				}
				else
				{
					sign = 1;
				}
				long gcd = gcd(numerator, denominator);
				result = new Fraction(sign * numerator / gcd, denominator / gcd);
			}
			return result;
		}

		public final long numerator;
		public final long denominator;

		private Fraction(long numerator, long denominator)
		{
			this.numerator = numerator;
			this.denominator = denominator;
		}

		public Fraction add(Fraction fraction)
		{
			return fraction(this.numerator * fraction.denominator + fraction.numerator * this.denominator, this.denominator * fraction.denominator);
		}

		@Override
		public int compareTo(Fraction that)
		{
			return Long.compare(this.numerator * that.denominator, that.numerator * this.denominator);
		}

		public Fraction divide(Fraction fraction)
		{
			return multiply(fraction.inverse());
		}

		public boolean equals(Fraction that)
		{
			return this.compareTo(that) == 0;
		}

		public boolean equals(Object that)
		{
			return this.compareTo((Fraction) that) == 0;
		}

		public Fraction getRemainder()
		{
			return fraction(this.numerator - getWholePart() * denominator, denominator);
		}

		public long getWholePart()
		{
			return this.numerator / this.denominator;
		}

		public Fraction inverse()
		{
			return fraction(this.denominator, this.numerator);
		}

		public Fraction multiply(Fraction fraction)
		{
			return fraction(this.numerator * fraction.numerator, this.denominator * fraction.denominator);
		}

		public Fraction neg()
		{
			return fraction(-this.numerator, this.denominator);
		}

		public Fraction sub(Fraction fraction)
		{
			return add(fraction.neg());
		}

		@Override
		public String toString()
		{
			String result;
			if (getRemainder().equals(Fraction.ZERO))
			{
				result = "" + this.numerator;
			}
			else
			{
				result = this.numerator + "/" + this.denominator;
			}
			return result;
		}
	}

	static class IteratorBuffer<Type>
	{
		private Iterator<Type> iterator;
		private List<Type> list;

		public IteratorBuffer(Iterator<Type> iterator)
		{
			this.iterator = iterator;
			this.list = new ArrayList<Type>();
		}

		public Iterator<Type> iterator()
		{
			return new Iterator<Type>()
			{
				int index = 0;

				@Override
				public boolean hasNext()
				{
					return this.index < list.size() || IteratorBuffer.this.iterator.hasNext();
				}

				@Override
				public Type next()
				{
					if (list.size() <= this.index)
					{
						list.add(iterator.next());
					}
					Type result = list.get(index);
					index += 1;
					return result;
				}
			};
		}
	}

	public static class MapCount<Type> extends SortedMapAVL<Type, Long>
	{
		private int count;

		public MapCount(Comparator<? super Type> comparator)
		{
			super(comparator);
			this.count = 0;
		}

		public long add(Type key, Long delta)
		{
			long result;
			if (delta > 0)
			{
				Long value = get(key);
				if (value == null)
				{
					value = delta;
				}
				else
				{
					value += delta;
				}
				put(key, value);
				result = delta;
			}
			else
			{
				result = 0;
			}
			this.count += result;
			return result;
		}

		public int count()
		{
			return this.count;
		}

		public List<Type> flatten()
		{
			List<Type> result = new ArrayList<>();
			for (Entry<Type, Long> entry : entrySet())
			{
				for (long index = 0; index < entry.getValue(); index++)
				{
					result.add(entry.getKey());
				}
			}
			return result;
		}

		@Override
		public SortedMapAVL<Type, Long> headMap(Type keyEnd)
		{
			throw new UnsupportedOperationException();
		}

		@Override
		public void putAll(Map<? extends Type, ? extends Long> map)
		{
			throw new UnsupportedOperationException();
		}

		public long remove(Type key, Long delta)
		{
			long result;
			if (delta > 0)
			{
				Long value = get(key) - delta;
				if (value <= 0)
				{
					result = delta + value;
					remove(key);
				}
				else
				{
					result = delta;
					put(key, value);
				}
			}
			else
			{
				result = 0;
			}
			this.count -= result;
			return result;
		}

		@Override
		public Long remove(Object key)
		{
			Long result = super.remove(key);
			this.count -= result;
			return result;
		}

		@Override
		public SortedMapAVL<Type, Long> subMap(Type keyStart, Type keyEnd)
		{
			throw new UnsupportedOperationException();
		}

		@Override
		public SortedMapAVL<Type, Long> tailMap(Type keyStart)
		{
			throw new UnsupportedOperationException();
		}
	}

	public static class MapSet<TypeKey, TypeValue> extends SortedMapAVL<TypeKey, SortedSetAVL<TypeValue>> implements Iterable<TypeValue>
	{
		private Comparator<? super TypeValue> comparatorValue;

		public MapSet(Comparator<? super TypeKey> comparatorKey, Comparator<? super TypeValue> comparatorValue)
		{
			super(comparatorKey);
			this.comparatorValue = comparatorValue;
		}

		public MapSet(Comparator<? super TypeKey> comparatorKey, SortedSetAVL<Entry<TypeKey, SortedSetAVL<TypeValue>>> entrySet, Comparator<? super TypeValue> comparatorValue)
		{
			super(comparatorKey, entrySet);
			this.comparatorValue = comparatorValue;
		}

		public boolean add(TypeKey key, TypeValue value)
		{
			SortedSetAVL<TypeValue> set = computeIfAbsent(key, k -> new SortedSetAVL<>(comparatorValue));
			return set.add(value);
		}

		public TypeValue firstValue()
		{
			TypeValue result;
			Entry<TypeKey, SortedSetAVL<TypeValue>> firstEntry = firstEntry();
			if (firstEntry == null)
			{
				result = null;
			}
			else
			{
				result = firstEntry.getValue().first();
			}
			return result;
		}

		@Override
		public MapSet<TypeKey, TypeValue> headMap(TypeKey keyEnd)
		{
			return new MapSet<>(this.comparator, this.entrySet.headSet(new AbstractMap.SimpleEntry<>(keyEnd, null)), this.comparatorValue);
		}

		public Iterator<TypeValue> iterator()
		{
			return new Iterator<TypeValue>()
			{
				Iterator<SortedSetAVL<TypeValue>> iteratorValues = values().iterator();
				Iterator<TypeValue> iteratorValue = null;

				@Override
				public boolean hasNext()
				{
					return iteratorValues.hasNext() || (iteratorValue != null && iteratorValue.hasNext());
				}

				@Override
				public TypeValue next()
				{
					if (iteratorValue == null || !iteratorValue.hasNext())
					{
						iteratorValue = iteratorValues.next().iterator();
					}
					return iteratorValue.next();
				}
			};
		}

		public TypeValue lastValue()
		{
			TypeValue result;
			Entry<TypeKey, SortedSetAVL<TypeValue>> lastEntry = lastEntry();
			if (lastEntry == null)
			{
				result = null;
			}
			else
			{
				result = lastEntry.getValue().last();
			}
			return result;
		}

		public boolean removeSet(TypeKey key, TypeValue value)
		{
			boolean result;
			SortedSetAVL<TypeValue> set = get(key);
			if (set == null)
			{
				result = false;
			}
			else
			{
				result = set.remove(value);
				if (set.size() == 0)
				{
					remove(key);
				}
			}
			return result;
		}

		@Override
		public MapSet<TypeKey, TypeValue> tailMap(TypeKey keyStart)
		{
			return new MapSet<>(this.comparator, this.entrySet.tailSet(new AbstractMap.SimpleEntry<>(keyStart, null)), this.comparatorValue);
		}
	}

	public static class Matrix
	{
		public final int rows;
		public final int columns;
		public final Fraction[][] cells;

		public Matrix(int rows, int columns)
		{
			this.rows = rows;
			this.columns = columns;
			this.cells = new Fraction[rows][columns];
			for (int row = 0; row < rows; row++)
			{
				for (int column = 0; column < columns; column++)
				{
					set(row, column, Fraction.ZERO);
				}
			}
		}

		public void add(int rowSource, int rowTarget, Fraction fraction)
		{
			for (int column = 0; column < columns; column++)
			{
				this.cells[rowTarget][column] = this.cells[rowTarget][column].add(this.cells[rowSource][column].multiply(fraction));
			}
		}

		private int columnPivot(int row)
		{
			int result = this.columns;
			for (int column = this.columns - 1; 0 <= column; column--)
			{
				if (this.cells[row][column].compareTo(Fraction.ZERO) != 0)
				{
					result = column;
				}
			}
			return result;
		}

		public void reduce()
		{
			for (int rowMinimum = 0; rowMinimum < this.rows; rowMinimum++)
			{
				int rowPivot = rowPivot(rowMinimum);
				if (rowPivot != -1)
				{
					int columnPivot = columnPivot(rowPivot);
					Fraction current = this.cells[rowMinimum][columnPivot];
					Fraction pivot = this.cells[rowPivot][columnPivot];
					Fraction fraction = pivot.inverse().sub(current.divide(pivot));
					add(rowPivot, rowMinimum, fraction);
					for (int row = rowMinimum + 1; row < this.rows; row++)
					{
						if (columnPivot(row) == columnPivot)
						{
							add(rowMinimum, row, this.cells[row][columnPivot(row)].neg());
						}
					}
				}
			}
		}

		private int rowPivot(int rowMinimum)
		{
			int result = -1;
			int pivotColumnMinimum = this.columns;
			for (int row = rowMinimum; row < this.rows; row++)
			{
				int pivotColumn = columnPivot(row);
				if (pivotColumn < pivotColumnMinimum)
				{
					result = row;
					pivotColumnMinimum = pivotColumn;
				}
			}
			return result;
		}

		public void set(int row, int column, Fraction value)
		{
			this.cells[row][column] = value;
		}

		public String toString()
		{
			String result = "";
			for (int row = 0; row < rows; row++)
			{
				for (int column = 0; column < columns; column++)
				{
					result += this.cells[row][column] + "\t";
				}
				result += "\n";
			}
			return result;
		}
	}

	public static class Node<Type>
	{
		public static <Type> Node<Type> balance(Node<Type> result)
		{
			while (result != null && 1 < Math.abs(height(result.left) - height(result.right)))
			{
				if (height(result.left) < height(result.right))
				{
					Node<Type> right = result.right;
					if (height(right.right) < height(right.left))
					{
						result = new Node<>(result.value, result.left, right.rotateRight());
					}
					result = result.rotateLeft();
				}
				else
				{
					Node<Type> left = result.left;
					if (height(left.left) < height(left.right))
					{
						result = new Node<>(result.value, left.rotateLeft(), result.right);
					}
					result = result.rotateRight();
				}
			}
			return result;
		}

		public static <Type> Node<Type> clone(Node<Type> result)
		{
			if (result != null)
			{
				result = new Node<>(result.value, clone(result.left), clone(result.right));
			}
			return result;
		}

		public static <Type> Node<Type> delete(Node<Type> node, Type value, Comparator<? super Type> comparator)
		{
			Node<Type> result;
			if (node == null)
			{
				result = null;
			}
			else
			{
				int compare = comparator.compare(value, node.value);
				if (compare == 0)
				{
					if (node.left == null)
					{
						result = node.right;
					}
					else
					{
						if (node.right == null)
						{
							result = node.left;
						}
						else
						{
							Node<Type> first = first(node.right);
							result = new Node<>(first.value, node.left, delete(node.right, first.value, comparator));
						}
					}
				}
				else
				{
					if (compare < 0)
					{
						result = new Node<>(node.value, delete(node.left, value, comparator), node.right);
					}
					else
					{
						result = new Node<>(node.value, node.left, delete(node.right, value, comparator));
					}
				}
				result = balance(result);
			}
			return result;
		}

		public static <Type> Node<Type> first(Node<Type> result)
		{
			while (result.left != null)
			{
				result = result.left;
			}
			return result;
		}

		public static <Type> Node<Type> get(Node<Type> node, Type value, Comparator<? super Type> comparator)
		{
			Node<Type> result;
			if (node == null)
			{
				result = null;
			}
			else
			{
				int compare = comparator.compare(value, node.value);
				if (compare == 0)
				{
					result = node;
				}
				else
				{
					if (compare < 0)
					{
						result = get(node.left, value, comparator);
					}
					else
					{
						result = get(node.right, value, comparator);
					}
				}
			}
			return result;
		}

		public static <Type> Node<Type> head(Node<Type> node, Type value, Comparator<? super Type> comparator)
		{
			Node<Type> result;
			if (node == null)
			{
				result = null;
			}
			else
			{
				int compare = comparator.compare(value, node.value);
				if (compare == 0)
				{
					result = node.left;
				}
				else
				{
					if (compare < 0)
					{
						result = head(node.left, value, comparator);
					}
					else
					{
						result = new Node<>(node.value, node.left, head(node.right, value, comparator));
					}
				}
				result = balance(result);
			}
			return result;
		}

		public static int height(Node node)
		{
			return node == null ? 0 : node.height;
		}

		public static <Type> Node<Type> insert(Node<Type> node, Type value, Comparator<? super Type> comparator)
		{
			Node<Type> result;
			if (node == null)
			{
				result = new Node<>(value, null, null);
			}
			else
			{
				int compare = comparator.compare(value, node.value);
				if (compare == 0)
				{
					result = new Node<>(value, node.left, node.right);
					;
				}
				else
				{
					if (compare < 0)
					{
						result = new Node<>(node.value, insert(node.left, value, comparator), node.right);
					}
					else
					{
						result = new Node<>(node.value, node.left, insert(node.right, value, comparator));
					}
				}
				result = balance(result);
			}
			return result;
		}

		public static <Type> Node<Type> last(Node<Type> result)
		{
			while (result.right != null)
			{
				result = result.right;
			}
			return result;
		}

		public static int size(Node node)
		{
			return node == null ? 0 : node.size;
		}

		public static <Type> Node<Type> tail(Node<Type> node, Type value, Comparator<? super Type> comparator)
		{
			Node<Type> result;
			if (node == null)
			{
				result = null;
			}
			else
			{
				int compare = comparator.compare(value, node.value);
				if (compare == 0)
				{
					result = new Node<>(node.value, null, node.right);
				}
				else
				{
					if (compare < 0)
					{
						result = new Node<>(node.value, tail(node.left, value, comparator), node.right);
					}
					else
					{
						result = tail(node.right, value, comparator);
					}
				}
				result = balance(result);
			}
			return result;
		}

		public static <Type> void traverseOrderIn(Node<Type> node, Consumer<Type> consumer)
		{
			if (node != null)
			{
				traverseOrderIn(node.left, consumer);
				consumer.accept(node.value);
				traverseOrderIn(node.right, consumer);
			}
		}

		public final Type value;
		public final Node<Type> left;
		public final Node<Type> right;
		public final int size;
		private final int height;

		public Node(Type value, Node<Type> left, Node<Type> right)
		{
			this.value = value;
			this.left = left;
			this.right = right;
			this.size = 1 + size(left) + size(right);
			this.height = 1 + Math.max(height(left), height(right));
		}

		public Node<Type> rotateLeft()
		{
			Node<Type> left = new Node<>(this.value, this.left, this.right.left);
			return new Node<>(this.right.value, left, this.right.right);
		}

		public Node<Type> rotateRight()
		{
			Node<Type> right = new Node<>(this.value, this.left.right, this.right);
			return new Node<>(this.left.value, this.left.left, right);
		}
	}

	public static class SingleLinkedList<Type>
	{
		public final Type element;
		public SingleLinkedList<Type> next;

		public SingleLinkedList(Type element, SingleLinkedList<Type> next)
		{
			this.element = element;
			this.next = next;
		}

		public void toCollection(Collection<Type> collection)
		{
			if (this.next != null)
			{
				this.next.toCollection(collection);
			}
			collection.add(this.element);
		}
	}

	public static class SmallSetIntegers
	{
		public static final int SIZE = 20;
		public static final int[] SET = generateSet();
		public static final int[] COUNT = generateCount();
		public static final int[] INTEGER = generateInteger();

		private static int count(int set)
		{
			int result = 0;
			for (int integer = 0; integer < SIZE; integer++)
			{
				if (0 < (set & set(integer)))
				{
					result += 1;
				}
			}
			return result;
		}

		private static final int[] generateCount()
		{
			int[] result = new int[1 << SIZE];
			for (int set = 0; set < result.length; set++)
			{
				result[set] = count(set);
			}
			return result;
		}

		private static final int[] generateInteger()
		{
			int[] result = new int[1 << SIZE];
			Arrays.fill(result, -1);
			for (int integer = 0; integer < SIZE; integer++)
			{
				result[SET[integer]] = integer;
			}
			return result;
		}

		private static final int[] generateSet()
		{
			int[] result = new int[SIZE];
			for (int integer = 0; integer < result.length; integer++)
			{
				result[integer] = set(integer);
			}
			return result;
		}

		private static int set(int integer)
		{
			return 1 << integer;
		}
	}

	public static class SortedMapAVL<TypeKey, TypeValue> implements SortedMap<TypeKey, TypeValue>
	{
		public final Comparator<? super TypeKey> comparator;
		public final SortedSetAVL<Entry<TypeKey, TypeValue>> entrySet;

		public SortedMapAVL(Comparator<? super TypeKey> comparator)
		{
			this(comparator, new SortedSetAVL<>((entry0, entry1) -> comparator.compare(entry0.getKey(), entry1.getKey())));
		}

		private SortedMapAVL(Comparator<? super TypeKey> comparator, SortedSetAVL<Entry<TypeKey, TypeValue>> entrySet)
		{
			this.comparator = comparator;
			this.entrySet = entrySet;
		}

		@Override
		public void clear()
		{
			this.entrySet.clear();
		}

		@Override
		public Comparator<? super TypeKey> comparator()
		{
			return this.comparator;
		}

		@Override
		public boolean containsKey(Object key)
		{
			return this.entrySet().contains(new AbstractMap.SimpleEntry<>((TypeKey) key, null));
		}

		@Override
		public boolean containsValue(Object value)
		{
			throw new UnsupportedOperationException();
		}

		@Override
		public SortedSetAVL<Entry<TypeKey, TypeValue>> entrySet()
		{
			return this.entrySet;
		}

		public Entry<TypeKey, TypeValue> firstEntry()
		{
			return this.entrySet.first();
		}

		@Override
		public TypeKey firstKey()
		{
			return firstEntry().getKey();
		}

		@Override
		public TypeValue get(Object key)
		{
			Entry<TypeKey, TypeValue> entry = new AbstractMap.SimpleEntry<>((TypeKey) key, null);
			entry = this.entrySet.get(entry);
			return entry == null ? null : entry.getValue();
		}

		@Override
		public SortedMapAVL<TypeKey, TypeValue> headMap(TypeKey keyEnd)
		{
			return new SortedMapAVL<>(this.comparator, this.entrySet.headSet(new AbstractMap.SimpleEntry<>(keyEnd, null)));
		}

		@Override
		public boolean isEmpty()
		{
			return this.entrySet.isEmpty();
		}

		@Override
		public Set<TypeKey> keySet()
		{
			return new SortedSet<TypeKey>()
			{
				@Override
				public boolean add(TypeKey typeKey)
				{
					throw new UnsupportedOperationException();
				}

				@Override
				public boolean addAll(Collection<? extends TypeKey> collection)
				{
					throw new UnsupportedOperationException();
				}

				@Override
				public void clear()
				{
					throw new UnsupportedOperationException();
				}

				@Override
				public Comparator<? super TypeKey> comparator()
				{
					throw new UnsupportedOperationException();
				}

				@Override
				public boolean contains(Object o)
				{
					throw new UnsupportedOperationException();
				}

				@Override
				public boolean containsAll(Collection<?> collection)
				{
					throw new UnsupportedOperationException();
				}

				@Override
				public TypeKey first()
				{
					throw new UnsupportedOperationException();
				}

				@Override
				public SortedSet<TypeKey> headSet(TypeKey typeKey)
				{
					throw new UnsupportedOperationException();
				}

				@Override
				public boolean isEmpty()
				{
					return size() == 0;
				}

				@Override
				public Iterator<TypeKey> iterator()
				{
					final Iterator<Entry<TypeKey, TypeValue>> iterator = SortedMapAVL.this.entrySet.iterator();
					return new Iterator<TypeKey>()
					{
						@Override
						public boolean hasNext()
						{
							return iterator.hasNext();
						}

						@Override
						public TypeKey next()
						{
							return iterator.next().getKey();
						}
					};
				}

				@Override
				public TypeKey last()
				{
					throw new UnsupportedOperationException();
				}

				@Override
				public boolean remove(Object o)
				{
					throw new UnsupportedOperationException();
				}

				@Override
				public boolean removeAll(Collection<?> collection)
				{
					throw new UnsupportedOperationException();
				}

				@Override
				public boolean retainAll(Collection<?> collection)
				{
					throw new UnsupportedOperationException();
				}

				@Override
				public int size()
				{
					return SortedMapAVL.this.entrySet.size();
				}

				@Override
				public SortedSet<TypeKey> subSet(TypeKey typeKey, TypeKey e1)
				{
					throw new UnsupportedOperationException();
				}

				@Override
				public SortedSet<TypeKey> tailSet(TypeKey typeKey)
				{
					throw new UnsupportedOperationException();
				}

				@Override
				public Object[] toArray()
				{
					throw new UnsupportedOperationException();
				}

				@Override
				public <T> T[] toArray(T[] ts)
				{
					throw new UnsupportedOperationException();
				}
			};
		}

		public Entry<TypeKey, TypeValue> lastEntry()
		{
			return this.entrySet.last();
		}

		@Override
		public TypeKey lastKey()
		{
			return lastEntry().getKey();
		}

		@Override
		public TypeValue put(TypeKey key, TypeValue value)
		{
			TypeValue result = get(key);
			Entry<TypeKey, TypeValue> entry = new AbstractMap.SimpleEntry<>(key, value);
			this.entrySet().add(entry);
			return result;
		}

		@Override
		public void putAll(Map<? extends TypeKey, ? extends TypeValue> map)
		{
			map.entrySet()
					.forEach(entry -> put(entry.getKey(), entry.getValue()));
		}

		@Override
		public TypeValue remove(Object key)
		{
			TypeValue result = get(key);
			Entry<TypeKey, TypeValue> entry = new AbstractMap.SimpleEntry<>((TypeKey) key, null);
			this.entrySet.remove(entry);
			return result;
		}

		@Override
		public int size()
		{
			return this.entrySet().size();
		}

		@Override
		public SortedMapAVL<TypeKey, TypeValue> subMap(TypeKey keyStart, TypeKey keyEnd)
		{
			return new SortedMapAVL<>(this.comparator, this.entrySet.subSet(new AbstractMap.SimpleEntry<>(keyStart, null), new AbstractMap.SimpleEntry<>(keyEnd, null)));
		}

		@Override
		public SortedMapAVL<TypeKey, TypeValue> tailMap(TypeKey keyStart)
		{
			return new SortedMapAVL<>(this.comparator, this.entrySet.tailSet(new AbstractMap.SimpleEntry<>(keyStart, null)));
		}

		@Override
		public String toString()
		{
			return this.entrySet().toString();
		}

		@Override
		public Collection<TypeValue> values()
		{
			return new Collection<TypeValue>()
			{
				@Override
				public boolean add(TypeValue typeValue)
				{
					throw new UnsupportedOperationException();
				}

				@Override
				public boolean addAll(Collection<? extends TypeValue> collection)
				{
					throw new UnsupportedOperationException();
				}

				@Override
				public void clear()
				{
					throw new UnsupportedOperationException();
				}

				@Override
				public boolean contains(Object value)
				{
					throw new UnsupportedOperationException();
				}

				@Override
				public boolean containsAll(Collection<?> collection)
				{
					throw new UnsupportedOperationException();
				}

				@Override
				public boolean isEmpty()
				{
					return SortedMapAVL.this.entrySet.isEmpty();
				}

				@Override
				public Iterator<TypeValue> iterator()
				{
					return new Iterator<TypeValue>()
					{
						Iterator<Entry<TypeKey, TypeValue>> iterator = SortedMapAVL.this.entrySet.iterator();

						@Override
						public boolean hasNext()
						{
							return this.iterator.hasNext();
						}

						@Override
						public TypeValue next()
						{
							return this.iterator.next().getValue();
						}
					};
				}

				@Override
				public boolean remove(Object o)
				{
					throw new UnsupportedOperationException();
				}

				@Override
				public boolean removeAll(Collection<?> collection)
				{
					throw new UnsupportedOperationException();
				}

				@Override
				public boolean retainAll(Collection<?> collection)
				{
					throw new UnsupportedOperationException();
				}

				@Override
				public int size()
				{
					return SortedMapAVL.this.entrySet.size();
				}

				@Override
				public Object[] toArray()
				{
					throw new UnsupportedOperationException();
				}

				@Override
				public <T> T[] toArray(T[] ts)
				{
					throw new UnsupportedOperationException();
				}
			};
		}
	}

	public static class SortedSetAVL<Type> implements SortedSet<Type>
	{
		public Comparator<? super Type> comparator;
		public Node<Type> root;

		private SortedSetAVL(Comparator<? super Type> comparator, Node<Type> root)
		{
			this.comparator = comparator;
			this.root = root;
		}

		public SortedSetAVL(Comparator<? super Type> comparator)
		{
			this(comparator, null);
		}

		public SortedSetAVL(Collection<? extends Type> collection, Comparator<? super Type> comparator)
		{
			this(comparator, null);
			this.addAll(collection);
		}

		public SortedSetAVL(SortedSetAVL<Type> sortedSetAVL)
		{
			this(sortedSetAVL.comparator, Node.clone(sortedSetAVL.root));
		}

		@Override
		public boolean add(Type value)
		{
			int sizeBefore = size();
			this.root = Node.insert(this.root, value, this.comparator);
			return sizeBefore != size();
		}

		@Override
		public boolean addAll(Collection<? extends Type> collection)
		{
			return collection.stream()
					.map(this::add)
					.reduce(true, (x, y) -> x | y);
		}

		@Override
		public void clear()
		{
			this.root = null;
		}

		@Override
		public Comparator<? super Type> comparator()
		{
			return this.comparator;
		}

		@Override
		public boolean contains(Object value)
		{
			return Node.get(this.root, (Type) value, this.comparator) != null;
		}

		@Override
		public boolean containsAll(Collection<?> collection)
		{
			return collection.stream()
					.allMatch(this::contains);
		}

		@Override
		public Type first()
		{
			return Node.first(this.root).value;
		}

		public Type get(Type value)
		{
			Node<Type> node = Node.get(this.root, value, this.comparator);
			return node == null ? null : node.value;
		}

		@Override
		public SortedSetAVL<Type> headSet(Type valueEnd)
		{
			return new SortedSetAVL<>(this.comparator, Node.head(this.root, valueEnd, this.comparator));
		}

		@Override
		public boolean isEmpty()
		{
			return this.root == null;
		}

		@Override
		public Iterator<Type> iterator()
		{
			Stack<Node<Type>> path = new Stack<>();
			return new Iterator<Type>()
			{
				{
					push(SortedSetAVL.this.root);
				}

				@Override
				public boolean hasNext()
				{
					return !path.isEmpty();
				}

				@Override
				public Type next()
				{
					if (path.isEmpty())
					{
						throw new NoSuchElementException();
					}
					else
					{
						Node<Type> node = path.peek();
						Type result = node.value;
						if (node.right != null)
						{
							push(node.right);
						}
						else
						{
							do
							{
								node = path.pop();
							}
							while (!path.isEmpty() && path.peek().right == node);
						}
						return result;
					}
				}

				public void push(Node<Type> node)
				{
					while (node != null)
					{
						path.push(node);
						node = node.left;
					}
				}
			};
		}

		@Override
		public Type last()
		{
			return Node.last(this.root).value;
		}

		@Override
		public boolean remove(Object value)
		{
			int sizeBefore = size();
			this.root = Node.delete(this.root, (Type) value, this.comparator);
			return sizeBefore != size();
		}

		@Override
		public boolean removeAll(Collection<?> collection)
		{
			return collection.stream()
					.map(this::remove)
					.reduce(true, (x, y) -> x | y);
		}

		@Override
		public boolean retainAll(Collection<?> collection)
		{
			SortedSetAVL<Type> set = new SortedSetAVL<>(this.comparator);
			collection.stream()
					.map(element -> (Type) element)
					.filter(this::contains)
					.forEach(set::add);
			boolean result = size() != set.size();
			this.root = set.root;
			return result;
		}

		@Override
		public int size()
		{
			return this.root == null ? 0 : this.root.size;
		}

		@Override
		public SortedSetAVL<Type> subSet(Type valueStart, Type valueEnd)
		{
			return tailSet(valueStart).headSet(valueEnd);
		}

		@Override
		public SortedSetAVL<Type> tailSet(Type valueStart)
		{
			return new SortedSetAVL<>(this.comparator, Node.tail(this.root, valueStart, this.comparator));
		}

		@Override
		public Object[] toArray()
		{
			return toArray(new Object[0]);
		}

		@Override
		public <T> T[] toArray(T[] ts)
		{
			List<Object> list = new ArrayList<>();
			Node.traverseOrderIn(this.root, list::add);
			return list.toArray(ts);
		}

		@Override
		public String toString()
		{
			return "{" + D_456.toString(this, ", ") + "}";
		}
	}

	public static class Tree2D
	{
		public static final int SIZE = 1 << 30;
		public static final Tree2D[] TREES_NULL = new Tree2D[] { null, null, null, null };

		public static boolean contains(int x, int y, int left, int bottom, int size)
		{
			return left <= x && x < left + size && bottom <= y && y < bottom + size;
		}

		public static int count(Tree2D[] trees)
		{
			int result = 0;
			for (int index = 0; index < 4; index++)
			{
				if (trees[index] != null)
				{
					result += trees[index].count;
				}
			}
			return result;
		}

		public static int count
				(
						int rectangleLeft,
						int rectangleBottom,
						int rectangleRight,
						int rectangleTop,
						Tree2D tree,
						int left,
						int bottom,
						int size
				)
		{
			int result;
			if (tree == null)
			{
				result = 0;
			}
			else
			{
				int right = left + size;
				int top = bottom + size;
				int intersectionLeft = Math.max(rectangleLeft, left);
				int intersectionBottom = Math.max(rectangleBottom, bottom);
				int intersectionRight = Math.min(rectangleRight, right);
				int intersectionTop = Math.min(rectangleTop, top);
				if (intersectionRight <= intersectionLeft || intersectionTop <= intersectionBottom)
				{
					result = 0;
				}
				else
				{
					if (intersectionLeft == left && intersectionBottom == bottom && intersectionRight == right && intersectionTop == top)
					{
						result = tree.count;
					}
					else
					{
						size = size >> 1;
						result = 0;
						for (int index = 0; index < 4; index++)
						{
							result += count
									(
											rectangleLeft,
											rectangleBottom,
											rectangleRight,
											rectangleTop,
											tree.trees[index],
											quadrantLeft(left, size, index),
											quadrantBottom(bottom, size, index),
											size
									);
						}
					}
				}
			}
			return result;
		}

		public static int quadrantBottom(int bottom, int size, int index)
		{
			return bottom + (index >> 1) * size;
		}

		public static int quadrantLeft(int left, int size, int index)
		{
			return left + (index & 1) * size;
		}

		public final Tree2D[] trees;
		public final int count;

		private Tree2D(Tree2D[] trees, int count)
		{
			this.trees = trees;
			this.count = count;
		}

		public Tree2D(Tree2D[] trees)
		{
			this(trees, count(trees));
		}

		public Tree2D()
		{
			this(TREES_NULL);
		}

		public int count(int rectangleLeft, int rectangleBottom, int rectangleRight, int rectangleTop)
		{
			return count
					(
							rectangleLeft,
							rectangleBottom,
							rectangleRight,
							rectangleTop,
							this,
							0,
							0,
							SIZE
					);
		}

		public Tree2D setPoint
				(
						int x,
						int y,
						Tree2D tree,
						int left,
						int bottom,
						int size
				)
		{
			Tree2D result;
			if (contains(x, y, left, bottom, size))
			{
				if (size == 1)
				{
					result = new Tree2D(TREES_NULL, 1);
				}
				else
				{
					size = size >> 1;
					Tree2D[] trees = new Tree2D[4];
					for (int index = 0; index < 4; index++)
					{
						trees[index] = setPoint
								(
										x,
										y,
										tree == null ? null : tree.trees[index],
										quadrantLeft(left, size, index),
										quadrantBottom(bottom, size, index),
										size
								);
					}
					result = new Tree2D(trees);
				}
			}
			else
			{
				result = tree;
			}
			return result;
		}

		public Tree2D setPoint(int x, int y)
		{
			return setPoint
					(
							x,
							y,
							this,
							0,
							0,
							SIZE
					);
		}
	}

	public static class Tuple2<Type0, Type1>
	{
		public final Type0 v0;
		public final Type1 v1;

		public Tuple2(Type0 v0, Type1 v1)
		{
			this.v0 = v0;
			this.v1 = v1;
		}

		@Override
		public String toString()
		{
			return "(" + this.v0 + ", " + this.v1 + ")";
		}
	}

	public static class Tuple2Comparable<Type0 extends Comparable<? super Type0>, Type1 extends Comparable<? super Type1>> extends Tuple2<Type0, Type1> implements Comparable<Tuple2Comparable<Type0, Type1>>
	{
		public Tuple2Comparable(Type0 v0, Type1 v1)
		{
			super(v0, v1);
		}

		@Override
		public int compareTo(Tuple2Comparable<Type0, Type1> that)
		{
			int result = this.v0.compareTo(that.v0);
			if (result == 0)
			{
				result = this.v1.compareTo(that.v1);
			}
			return result;
		}
	}

	public static class Tuple3<Type0, Type1, Type2>
	{
		public final Type0 v0;
		public final Type1 v1;
		public final Type2 v2;

		public Tuple3(Type0 v0, Type1 v1, Type2 v2)
		{
			this.v0 = v0;
			this.v1 = v1;
			this.v2 = v2;
		}

		@Override
		public String toString()
		{
			return "(" + this.v0 + ", " + this.v1 + ", " + this.v2 + ")";
		}
	}

	public static class Vertex
			<
					TypeVertex extends Vertex<TypeVertex, TypeEdge>,
					TypeEdge extends Edge<TypeVertex, TypeEdge>
					>
			implements Comparable<Vertex<? super TypeVertex, ? super TypeEdge>>
	{
		public static <
				TypeVertex extends Vertex<TypeVertex, TypeEdge>,
				TypeEdge extends Edge<TypeVertex, TypeEdge>,
				TypeResult
				> TypeResult breadthFirstSearch
				(
						TypeVertex vertex,
						TypeEdge edge,
						BiFunctionResult<TypeVertex, TypeEdge, TypeResult> function,
						Array<Boolean> visited,
						FIFO<TypeVertex> verticesNext,
						FIFO<TypeEdge> edgesNext,
						TypeResult result
				)
		{
			if (!visited.get(vertex.index))
			{
				visited.set(vertex.index, true);
				result = function.apply(vertex, edge, result);
				for (TypeEdge edgeNext : vertex.edges)
				{
					TypeVertex vertexNext = edgeNext.other(vertex);
					if (!visited.get(vertexNext.index))
					{
						verticesNext.push(vertexNext);
						edgesNext.push(edgeNext);
					}
				}
			}
			return result;
		}

		public static <
				TypeVertex extends Vertex<TypeVertex, TypeEdge>,
				TypeEdge extends Edge<TypeVertex, TypeEdge>,
				TypeResult
				>
		TypeResult breadthFirstSearch
				(
						Array<TypeVertex> vertices,
						int indexVertexStart,
						BiFunctionResult<TypeVertex, TypeEdge, TypeResult> function,
						TypeResult result
				)
		{
			Array<Boolean> visited = new Array<>(vertices.size(), false);
			FIFO<TypeVertex> verticesNext = new FIFO<>();
			verticesNext.push(vertices.get(indexVertexStart));
			FIFO<TypeEdge> edgesNext = new FIFO<>();
			edgesNext.push(null);
			while (!verticesNext.isEmpty())
			{
				result = breadthFirstSearch(verticesNext.pop(), edgesNext.pop(), function, visited, verticesNext, edgesNext, result);
			}
			return result;
		}

		public static <
				TypeVertex extends Vertex<TypeVertex, TypeEdge>,
				TypeEdge extends Edge<TypeVertex, TypeEdge>
				>
		boolean
		cycle
				(
						TypeVertex start,
						SortedSet<TypeVertex> result
				)
		{
			boolean cycle = false;
			Stack<TypeVertex> stackVertex = new Stack<>();
			Stack<TypeEdge> stackEdge = new Stack<>();
			stackVertex.push(start);
			stackEdge.push(null);
			while (!stackVertex.isEmpty())
			{
				TypeVertex vertex = stackVertex.pop();
				TypeEdge edge = stackEdge.pop();
				if (!result.contains(vertex))
				{
					result.add(vertex);
					for (TypeEdge otherEdge : vertex.edges)
					{
						if (otherEdge != edge)
						{
							TypeVertex otherVertex = otherEdge.other(vertex);
							if (result.contains(otherVertex))
							{
								cycle = true;
							}
							else
							{
								stackVertex.push(otherVertex);
								stackEdge.push(otherEdge);
							}
						}
					}
				}
			}
			return cycle;
		}

		public static <
				TypeVertex extends Vertex<TypeVertex, TypeEdge>,
				TypeEdge extends Edge<TypeVertex, TypeEdge>
				>
		SortedSet<TypeVertex>
		depthFirstSearch
				(
						TypeVertex start,
						BiConsumer<TypeVertex, TypeEdge> functionVisitPre,
						BiConsumer<TypeVertex, TypeEdge> functionVisitPost
				)
		{
			SortedSet<TypeVertex> result = new SortedSetAVL<>(Comparator.naturalOrder());
			Stack<TypeVertex> stackVertex = new Stack<>();
			Stack<TypeEdge> stackEdge = new Stack<>();
			stackVertex.push(start);
			stackEdge.push(null);
			while (!stackVertex.isEmpty())
			{
				TypeVertex vertex = stackVertex.pop();
				TypeEdge edge = stackEdge.pop();
				if (result.contains(vertex))
				{
					functionVisitPost.accept(vertex, edge);
				}
				else
				{
					result.add(vertex);
					stackVertex.push(vertex);
					stackEdge.push(edge);
					functionVisitPre.accept(vertex, edge);
					for (TypeEdge otherEdge : vertex.edges)
					{
						TypeVertex otherVertex = otherEdge.other(vertex);
						if (!result.contains(otherVertex))
						{
							stackVertex.push(otherVertex);
							stackEdge.push(otherEdge);
						}
					}
				}
			}
			return result;
		}

		public static <
				TypeVertex extends Vertex<TypeVertex, TypeEdge>,
				TypeEdge extends Edge<TypeVertex, TypeEdge>
				>
		SortedSet<TypeVertex>
		depthFirstSearch
				(
						TypeVertex start,
						Consumer<TypeVertex> functionVisitPreVertex,
						Consumer<TypeVertex> functionVisitPostVertex
				)
		{
			BiConsumer<TypeVertex, TypeEdge> functionVisitPreVertexEdge = (vertex, edge) ->
			{
				functionVisitPreVertex.accept(vertex);
			};
			BiConsumer<TypeVertex, TypeEdge> functionVisitPostVertexEdge = (vertex, edge) ->
			{
				functionVisitPostVertex.accept(vertex);
			};
			return depthFirstSearch(start, functionVisitPreVertexEdge, functionVisitPostVertexEdge);
		}

		public final int index;
		public final List<TypeEdge> edges;

		public Vertex(int index)
		{
			this.index = index;
			this.edges = new ArrayList<>();
		}

		@Override
		public int compareTo(Vertex<? super TypeVertex, ? super TypeEdge> that)
		{
			return Integer.compare(this.index, that.index);
		}

		@Override
		public String toString()
		{
			return "" + this.index;
		}
	}

	public static class VertexDefault<TypeEdge extends Edge<VertexDefault<TypeEdge>, TypeEdge>> extends Vertex<VertexDefault<TypeEdge>, TypeEdge>
	{
		public VertexDefault(int index)
		{
			super(index);
		}
	}

	public static class VertexDefaultDefault extends Vertex<VertexDefaultDefault, EdgeDefaultDefault>
	{
		public static Array<VertexDefaultDefault> vertices(int n)
		{
			Array<VertexDefaultDefault> result = new Array<>(n);
			for (int index = 0; index < n; index++)
			{
				result.set(index, new VertexDefaultDefault(index));
			}
			return result;
		}

		public VertexDefaultDefault(int index)
		{
			super(index);
		}
	}

	public static class Wrapper<Type>
	{
		public Type value;

		public Wrapper(Type value)
		{
			this.value = value;
		}

		public Type get()
		{
			return this.value;
		}

		public void set(Type value)
		{
			this.value = value;
		}

		@Override
		public String toString()
		{
			return this.value.toString();
		}
	}

	public static void add(int delta, int[] result)
	{
		for (int index = 0; index < result.length; index++)
		{
			result[index] += delta;
		}
	}

	public static void add(int delta, int[]... result)
	{
		for (int index = 0; index < result.length; index++)
		{
			add(delta, result[index]);
		}
	}

	public static int binarySearchMaximum(Function<Integer, Boolean> filter, int start, int end)
	{
		return -binarySearchMinimum(x -> filter.apply(-x), -end, -start);
	}

	public static int binarySearchMinimum(Function<Integer, Boolean> filter, int start, int end)
	{
		int result;
		if (start == end)
		{
			result = end;
		}
		else
		{
			int middle = start + (end - start) / 2;
			if (filter.apply(middle))
			{
				result = binarySearchMinimum(filter, start, middle);
			}
			else
			{
				result = binarySearchMinimum(filter, middle + 1, end);
			}
		}
		return result;
	}

	public static void close()
	{
		out.close();
	}

	public static List<List<Integer>> combinations(int n, int k)
	{
		List<List<Integer>> result = new ArrayList<>();
		if (k == 0)
		{
		}
		else
		{
			if (k == 1)
			{
				List<Integer> combination = new ArrayList<>();
				combination.add(n);
				result.add(combination);
			}
			else
			{
				for (int index = 0; index <= n; index++)
				{
					for (List<Integer> combination : combinations(n - index, k - 1))
					{
						combination.add(index);
						result.add(combination);
					}
				}
			}
		}
		return result;
	}

	public static <Type> int compare(Iterator<Type> iterator0, Iterator<Type> iterator1, Comparator<Type> comparator)
	{
		int result = 0;
		while (result == 0 && iterator0.hasNext() && iterator1.hasNext())
		{
			result = comparator.compare(iterator0.next(), iterator1.next());
		}
		if (result == 0)
		{
			if (iterator1.hasNext())
			{
				result = -1;
			}
			else
			{
				if (iterator0.hasNext())
				{
					result = 1;
				}
			}
		}
		return result;
	}

	public static <Type> int compare(Iterable<Type> iterable0, Iterable<Type> iterable1, Comparator<Type> comparator)
	{
		return compare(iterable0.iterator(), iterable1.iterator(), comparator);
	}

	public static long divideCeil(long x, long y)
	{
		return (x + y - 1) / y;
	}

	public static Set<Long> divisors(long n)
	{
		SortedSetAVL<Long> result = new SortedSetAVL<>(Comparator.naturalOrder());
		result.add(1L);
		for (Long factor : factors(n))
		{
			SortedSetAVL<Long> divisors = new SortedSetAVL<>(result);
			for (Long divisor : result)
			{
				divisors.add(divisor * factor);
			}
			result = divisors;
		}
		return result;
	}

	public static LinkedList<Long> factors(long n)
	{
		LinkedList<Long> result = new LinkedList<>();
		Iterator<Long> primes = ITERATOR_BUFFER_PRIME.iterator();
		Long prime;
		while (n > 1 && (prime = primes.next()) * prime <= n)
		{
			while (n % prime == 0)
			{
				result.add(prime);
				n /= prime;
			}
		}
		if (n > 1)
		{
			result.add(n);
		}
		return result;
	}

	public static long faculty(int n)
	{
		long result = 1;
		for (int index = 2; index <= n; index++)
		{
			result *= index;
		}
		return result;
	}

	public static long gcd(long a, long b)
	{
		while (a != 0 && b != 0)
		{
			if (a > b)
			{
				a %= b;
			}
			else
			{
				b %= a;
			}
		}
		return a + b;
	}

	public static long[] generatePOWER2()
	{
		long[] result = new long[63];
		for (int x = 0; x < result.length; x++)
		{
			result[x] = 1L << x;
		}
		return result;
	}

	public static boolean isPrime(long x)
	{
		boolean result = x > 1;
		Iterator<Long> iterator = ITERATOR_BUFFER_PRIME.iterator();
		Long prime;
		while ((prime = iterator.next()) * prime <= x)
		{
			result &= x % prime > 0;
		}
		return result;
	}

	public static long knapsack(List<Tuple3<Long, Integer, Integer>> itemsValueWeightCount, int weightMaximum)
	{
		long[] valuesMaximum = new long[weightMaximum + 1];
		for (Tuple3<Long, Integer, Integer> itemValueWeightCount : itemsValueWeightCount)
		{
			long itemValue = itemValueWeightCount.v0;
			int itemWeight = itemValueWeightCount.v1;
			int itemCount = itemValueWeightCount.v2;
			for (int weight = weightMaximum; 0 <= weight; weight--)
			{
				for (int index = 1; index <= itemCount && 0 <= weight - index * itemWeight; index++)
				{
					valuesMaximum[weight] = Math.max(valuesMaximum[weight], valuesMaximum[weight - index * itemWeight] + index * itemValue);
				}
			}
		}
		long result = 0;
		for (long valueMaximum : valuesMaximum)
		{
			result = Math.max(result, valueMaximum);
		}
		return result;
	}

	public static boolean knapsackPossible(List<Tuple2<Integer, Integer>> itemsWeightCount, int weightMaximum)
	{
		boolean[] weightPossible = new boolean[weightMaximum + 1];
		weightPossible[0] = true;
		int weightLargest = 0;
		for (Tuple2<Integer, Integer> itemWeightCount : itemsWeightCount)
		{
			int itemWeight = itemWeightCount.v0;
			int itemCount = itemWeightCount.v1;
			for (int weightStart = 0; weightStart < itemWeight; weightStart++)
			{
				int count = 0;
				for (int weight = weightStart; weight <= weightMaximum && (0 < count || weight <= weightLargest); weight += itemWeight)
				{
					if (weightPossible[weight])
					{
						count = itemCount;
					}
					else
					{
						if (0 < count)
						{
							weightPossible[weight] = true;
							weightLargest = weight;
							count -= 1;
						}
					}
				}
			}
		}
		return weightPossible[weightMaximum];
	}

	public static long lcm(int a, int b)
	{
		return a * b / gcd(a, b);
	}

	public static void main(String[] args)
	{
		try
		{
			solve();
		}
		catch (IOException exception)
		{
			exception.printStackTrace();
		}
		close();
	}

	public static double nextDouble() throws IOException
	{
		return Double.parseDouble(nextString());
	}

	public static int nextInt() throws IOException
	{
		return Integer.parseInt(nextString());
	}

	public static void nextInts(int n, int[]... result) throws IOException
	{
		for (int index = 0; index < n; index++)
		{
			for (int value = 0; value < result.length; value++)
			{
				result[value][index] = nextInt();
			}
		}
	}

	public static int[] nextInts(int n) throws IOException
	{
		int[] result = new int[n];
		nextInts(n, result);
		return result;
	}

	public static String nextLine() throws IOException
	{
		return bufferedReader.readLine();
	}

	public static long nextLong() throws IOException
	{
		return Long.parseLong(nextString());
	}

	public static void nextLongs(int n, long[]... result) throws IOException
	{
		for (int index = 0; index < n; index++)
		{
			for (int value = 0; value < result.length; value++)
			{
				result[value][index] = nextLong();
			}
		}
	}

	public static long[] nextLongs(int n) throws IOException
	{
		long[] result = new long[n];
		nextLongs(n, result);
		return result;
	}

	public static String nextString() throws IOException
	{
		while ((stringTokenizer == null) || (!stringTokenizer.hasMoreTokens()))
		{
			stringTokenizer = new StringTokenizer(bufferedReader.readLine());
		}
		return stringTokenizer.nextToken();
	}

	public static String[] nextStrings(int n) throws IOException
	{
		String[] result = new String[n];
		{
			for (int index = 0; index < n; index++)
			{
				result[index] = nextString();
			}
		}
		return result;
	}

	public static <T> List<T> permutation(long p, List<T> x)
	{
		List<T> copy = new ArrayList<>();
		for (int index = 0; index < x.size(); index++)
		{
			copy.add(x.get(index));
		}
		List<T> result = new ArrayList<>();
		for (int indexTo = 0; indexTo < x.size(); indexTo++)
		{
			int indexFrom = (int) p % copy.size();
			p = p / copy.size();
			result.add(copy.remove(indexFrom));
		}
		return result;
	}

	public static <Type> List<List<Type>> permutations(List<Type> list)
	{
		List<List<Type>> result = new ArrayList<>();
		result.add(new ArrayList<>());
		for (Type element : list)
		{
			List<List<Type>> permutations = result;
			result = new ArrayList<>();
			for (List<Type> permutation : permutations)
			{
				for (int index = 0; index <= permutation.size(); index++)
				{
					List<Type> permutationNew = new ArrayList<>(permutation);
					permutationNew.add(index, element);
					result.add(permutationNew);
				}
			}
		}
		return result;
	}

	public static Stream<BigInteger> streamFibonacci()
	{
		return Stream.generate(new Supplier<BigInteger>()
		{
			private BigInteger n0 = BigInteger.ZERO;
			private BigInteger n1 = BigInteger.ONE;

			@Override
			public BigInteger get()
			{
				BigInteger result = n0;
				n0 = n1;
				n1 = result.add(n0);
				return result;
			}
		});
	}

	public static Stream<Long> streamPrime(int sieveSize)
	{
		return Stream.generate(new Supplier<Long>()
		{
			private boolean[] isPrime = new boolean[sieveSize];
			private long sieveOffset = 2;
			private List<Long> primes = new ArrayList<>();
			private int index = 0;

			public void filter(long prime, boolean[] result)
			{
				if (prime * prime < this.sieveOffset + sieveSize)
				{
					long remainingStart = this.sieveOffset % prime;
					long start = remainingStart == 0 ? 0 : prime - remainingStart;
					for (long index = start; index < sieveSize; index += prime)
					{
						result[(int) index] = false;
					}
				}
			}

			public void generatePrimes()
			{
				Arrays.fill(this.isPrime, true);
				this.primes.forEach(prime -> filter(prime, isPrime));
				for (int index = 0; index < sieveSize; index++)
				{
					if (isPrime[index])
					{
						this.primes.add(this.sieveOffset + index);
						filter(this.sieveOffset + index, isPrime);
					}
				}
				this.sieveOffset += sieveSize;
			}

			@Override
			public Long get()
			{
				while (this.primes.size() <= this.index)
				{
					generatePrimes();
				}
				Long result = this.primes.get(this.index);
				this.index += 1;
				return result;
			}
		});
	}

	public static <Type> String toString(Iterator<Type> iterator, String separator)
	{
		StringBuilder stringBuilder = new StringBuilder();
		if (iterator.hasNext())
		{
			stringBuilder.append(iterator.next());
		}
		while (iterator.hasNext())
		{
			stringBuilder.append(separator);
			stringBuilder.append(iterator.next());
		}
		return stringBuilder.toString();
	}

	public static <Type> String toString(Iterator<Type> iterator)
	{
		return toString(iterator, " ");
	}

	public static <Type> String toString(Iterable<Type> iterable, String separator)
	{
		return toString(iterable.iterator(), separator);
	}

	public static <Type> String toString(Iterable<Type> iterable)
	{
		return toString(iterable, " ");
	}

	public static long totient(long n)
	{
		Set<Long> factors = new SortedSetAVL<>(factors(n), Comparator.naturalOrder());
		long result = n;
		for (long p : factors)
		{
			result -= result / p;
		}
		return result;
	}

	interface BiFunctionResult<Type0, Type1, TypeResult>
	{
		TypeResult apply(Type0 x0, Type1 x1, TypeResult x2);
	}

	static class Point implements Comparable<Point>
	{
		public static long n;
		public static long m;
		public static long r;
		public final long x;
		public final long y;

		public Point(long x, long y)
		{
			this.x = x;
			this.y = y;
		}

		public static long countOneDirection(long nm, long r, long xy)
		{
			return Math.min(nm - r + 1, Math.min(r, Math.min(xy + 1, nm - xy)));
		}

		public long count()
		{
			long countX = countOneDirection(n, r, this.x);
			long countY = countOneDirection(m, r, this.y);
			return countX * countY;
		}

		@Override
		public int compareTo(Point that)
		{
			int result = Long.compare(this.count(), that.count());
			if (result == 0)
			{
				result = Long.compare(this.x, that.x);
				if (result == 0)
				{
					result = Long.compare(this.y, that.y);
				}
			}
			return result;
		}

		@Override
		public String toString()
		{
			return "(" + this.x + ", " + this.y + ")";
		}
	}

	public static void solve() throws IOException
	{
		Point.n = nextInt();
		Point.m = nextInt();
		Point.r = nextInt();
		long k = nextInt();
		long total = (Point.n + 1 - Point.r) * (Point.m + 1 - Point.r);
		long count = 0;
		SortedSet<Point> done = new SortedSetAVL<>(Comparator.naturalOrder());
		SortedSet<Point> active = new SortedSetAVL<>(Comparator.naturalOrder());
		Point mid = new Point(Point.n / 2, Point.m / 2);
		active.add(mid);
		while (0 < k)
		{
			k -= 1;
			Point point = active.last();
			active.remove(point);
			done.add(point);
			count += point.count();
			if (0 < point.x)
			{
				Point pointNext = new Point(point.x - 1, point.y);
				if (!done.contains(pointNext))
				{
					active.add(pointNext);
				}
			}
			if (0 < point.y)
			{
				Point pointNext = new Point(point.x, point.y - 1);
				if (!done.contains(pointNext))
				{
					active.add(pointNext);
				}
			}
			if (point.x < Point.n - 1)
			{
				Point pointNext = new Point(point.x + 1, point.y);
				if (!done.contains(pointNext))
				{
					active.add(pointNext);
				}
			}
			if (point.y < Point.m - 1)
			{
				Point pointNext = new Point(point.x, point.y + 1);
				if (!done.contains(pointNext))
				{
					active.add(pointNext);
				}
			}
		}
		out.println((double) count / total);
	}
}