Problem:
Score : 1300 points

Problem Statement

You are playing a game and your goal is to maximize your expected gain.
At the beginning of the game, a pawn is put, uniformly at random, at a position p\in\{1,2,\dots, N\}. The N positions are arranged on a circle (so that 1 is between N and 2).

The game consists of turns. At each turn you can either end the game, and get A_p dollars (where p is the current position of the pawn), or pay B_p dollar to keep playing.
If you decide to keep playing, the pawn is randomly moved to one of the two adjacent positions p-1, p+1 (with the identifications 0 = N and N+1=1).

What is the expected gain of an optimal strategy?

Note: The "expected gain of an optimal strategy" shall be defined as the supremum of the expected gain among all strategies such that the game ends in a finite number of turns.

Constraints

2 \le N \le 200,000

0 \le A_p \le 10^{12} for any p = 1,\ldots, N

0 \le B_p \le 100 for any p = 1, \ldots, N

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N
A_1 A_2 \cdots A_N
B_1 B_2 \cdots B_N

Output

Print a single real number, the expected gain of an optimal strategy.
Your answer will be considered correct if its relative or absolute error does not exceed 10^{-10}.

Sample Input 1

5
4 2 6 3 5
1 1 1 1 1

Sample Output 1

4.700000000000

Sample Input 2

4
100 0 100 0
0 100 0 100

Sample Output 2

50.000000000000

Sample Input 3

14
4839 5400 6231 5800 6001 5200 6350 7133 7986 8012 7537 7013 6477 5912
34 54 61 32 52 61 21 43 65 12 45 21 1 4

Sample Output 3

7047.142857142857

Sample Input 4

10
470606482521 533212137322 116718867454 746976621474 457112271419 815899162072 641324977314 88281100571 9231169966 455007126951
26 83 30 59 100 88 84 91 54 61

Sample Output 4

815899161079.400024414062

Solution in Java (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintStream;
import java.util.Arrays;
import java.io.IOException;
import java.io.UncheckedIOException;
import java.math.BigDecimal;
import java.io.Closeable;
import java.io.Writer;
import java.io.OutputStreamWriter;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) throws Exception {
        Thread thread = new Thread(null, new TaskAdapter(), "", 1 << 27);
        thread.start();
        thread.join();
    }

    static class TaskAdapter implements Runnable {
        @Override
        public void run() {
            InputStream inputStream = System.in;
            OutputStream outputStream = System.out;
            FastInput in = new FastInput(inputStream);
            FastOutput out = new FastOutput(outputStream);
            ERandomPawn solver = new ERandomPawn();
            solver.solve(1, in, out);
            out.close();
        }
    }

    static class ERandomPawn {
        Debug debug = new Debug(false);

        public void solve(int testNumber, FastInput in, FastOutput out) {
            int n = in.readInt();
            long[] a = new long[n];
            long[] b = new long[n];

            in.populate(a);
            in.populate(b);

            int maxIndex = 0;
            for (int i = 0; i < n; i++) {
                if (a[i] > a[maxIndex]) {
                    maxIndex = i;
                }
            }

            SequenceUtils.rotate(a, 0, n - 1, n - maxIndex);
            SequenceUtils.rotate(b, 0, n - 1, n - maxIndex);

            a = Arrays.copyOf(a, n + 1);
            b = Arrays.copyOf(b, n + 1);

            a[n] = a[0];
            b[n] = b[0];

            long[] c = new long[n + 1];
            c[0] = 0;
            c[1] = 0;
            for (int i = 2; i <= n; i++) {
                c[i] = 2 * c[i - 1] - c[i - 2] + 2 * b[i - 1];
            }

            debug.debug("a", a);
            debug.debug("b", b);
            debug.debug("c", c);

            double[] heights = new double[n + 1];
            for (int i = 0; i <= n; i++) {
                heights[i] = a[i] - c[i];
            }

            debug.debug("heights", heights);

            double[] y = ConvexHullAssignProblem.solve(heights);


            debug.debug("y", y);
            double[] x = new double[n + 1];
            for (int i = 0; i <= n; i++) {
                x[i] = y[i] + c[i];
            }

//        for (int i = 0; i <= n; i++) {
//            if (i == 0 || i == n) {
//                if(!isZero(y[i] - heights[i])){
//                    throw new RuntimeException();
//                }
//            }else{
//                if(!isZero(y[i] - Math.max(heights[i], (y[i - 1] + y[i + 1]) / 2))){
//                    throw new RuntimeException();
//                }
//            }
//        }


            debug.debug("x", x);
//        for (int i = 0; i <= n; i++) {
//            if (i == 0 || i == n) {
//                if(!isZero(x[i] - a[i])){
//                    throw new RuntimeException();
//                }
//            }else{
//                if(!isZero(x[i] - Math.max(a[i], (x[i - 1] + x[i + 1]) / 2 - b[i]))){
//                    throw new RuntimeException();
//                }
//            }
//        }

            double sum = 0;
            for (int i = 0; i < n; i++) {
                sum += x[i] / n;
            }

            out.println(sum);
        }

    }

    static interface IntegerIterator {
        boolean hasNext();

        int next();

    }

    static class FastInput {
        private final InputStream is;
        private byte[] buf = new byte[1 << 13];
        private int bufLen;
        private int bufOffset;
        private int next;

        public FastInput(InputStream is) {
            this.is = is;
        }

        public void populate(long[] data) {
            for (int i = 0; i < data.length; i++) {
                data[i] = readLong();
            }
        }

        private int read() {
            while (bufLen == bufOffset) {
                bufOffset = 0;
                try {
                    bufLen = is.read(buf);
                } catch (IOException e) {
                    bufLen = -1;
                }
                if (bufLen == -1) {
                    return -1;
                }
            }
            return buf[bufOffset++];
        }

        public void skipBlank() {
            while (next >= 0 && next <= 32) {
                next = read();
            }
        }

        public int readInt() {
            int sign = 1;

            skipBlank();
            if (next == '+' || next == '-') {
                sign = next == '+' ? 1 : -1;
                next = read();
            }

            int val = 0;
            if (sign == 1) {
                while (next >= '0' && next <= '9') {
                    val = val * 10 + next - '0';
                    next = read();
                }
            } else {
                while (next >= '0' && next <= '9') {
                    val = val * 10 - next + '0';
                    next = read();
                }
            }

            return val;
        }

        public long readLong() {
            int sign = 1;

            skipBlank();
            if (next == '+' || next == '-') {
                sign = next == '+' ? 1 : -1;
                next = read();
            }

            long val = 0;
            if (sign == 1) {
                while (next >= '0' && next <= '9') {
                    val = val * 10 + next - '0';
                    next = read();
                }
            } else {
                while (next >= '0' && next <= '9') {
                    val = val * 10 - next + '0';
                    next = read();
                }
            }

            return val;
        }

    }

    static interface IntegerStack {
    }

    static class IntegerDequeImpl implements IntegerDeque {
        private int[] data;
        private int bpos;
        private int epos;
        private static final int[] EMPTY = new int[0];
        private int n;

        public IntegerDequeImpl(int cap) {
            if (cap == 0) {
                data = EMPTY;
            } else {
                data = new int[cap];
            }
            bpos = 0;
            epos = 0;
            n = cap;
        }

        private void expandSpace(int len) {
            while (n < len) {
                n = Math.max(n + 10, n * 2);
            }
            int[] newData = new int[n];
            if (bpos <= epos) {
                if (bpos < epos) {
                    System.arraycopy(data, bpos, newData, 0, epos - bpos);
                }
            } else {
                System.arraycopy(data, bpos, newData, 0, data.length - bpos);
                System.arraycopy(data, 0, newData, data.length - bpos, epos);
            }
            epos = size();
            bpos = 0;
            data = newData;
        }

        public IntegerIterator iterator() {
            return new IntegerIterator() {
                int index = bpos;


                public boolean hasNext() {
                    return index != epos;
                }


                public int next() {
                    int ans = data[index];
                    index = IntegerDequeImpl.this.next(index);
                    return ans;
                }
            };
        }

        public int removeLast() {
            int ans = data[last(epos)];
            epos = last(epos);
            return ans;
        }

        public void addLast(int x) {
            ensureMore();
            data[epos] = x;
            epos = next(epos);
        }

        public int peekLast() {
            return data[last(epos)];
        }

        private int last(int x) {
            return (x == 0 ? n : x) - 1;
        }

        private int next(int x) {
            return x + 1 >= n ? 0 : x + 1;
        }

        private void ensureMore() {
            if (next(epos) == bpos) {
                expandSpace(n + 1);
            }
        }

        public int size() {
            int ans = epos - bpos;
            if (ans < 0) {
                ans += data.length;
            }
            return ans;
        }

        public String toString() {
            StringBuilder builder = new StringBuilder();
            for (IntegerIterator iterator = iterator(); iterator.hasNext(); ) {
                builder.append(iterator.next()).append(' ');
            }
            return builder.toString();
        }

    }

    static class FastOutput implements AutoCloseable, Closeable, Appendable {
        private StringBuilder cache = new StringBuilder(10 << 20);
        private final Writer os;

        public FastOutput append(CharSequence csq) {
            cache.append(csq);
            return this;
        }

        public FastOutput append(CharSequence csq, int start, int end) {
            cache.append(csq, start, end);
            return this;
        }

        public FastOutput(Writer os) {
            this.os = os;
        }

        public FastOutput(OutputStream os) {
            this(new OutputStreamWriter(os));
        }

        public FastOutput append(char c) {
            cache.append(c);
            return this;
        }

        public FastOutput append(double c) {
            cache.append(new BigDecimal(c).toPlainString());
            return this;
        }

        public FastOutput println(double c) {
            return append(c).println();
        }

        public FastOutput println() {
            cache.append(System.lineSeparator());
            return this;
        }

        public FastOutput flush() {
            try {
                os.append(cache);
                os.flush();
                cache.setLength(0);
            } catch (IOException e) {
                throw new UncheckedIOException(e);
            }
            return this;
        }

        public void close() {
            flush();
            try {
                os.close();
            } catch (IOException e) {
                throw new UncheckedIOException(e);
            }
        }

        public String toString() {
            return cache.toString();
        }

    }

    static class Debug {
        private boolean offline;
        private PrintStream out = System.err;
        static int[] empty = new int[0];

        public Debug(boolean enable) {
            offline = enable && System.getSecurityManager() == null;
        }

        public Debug debug(String name, Object x) {
            return debug(name, x, empty);
        }

        public Debug debug(String name, Object x, int... indexes) {
            if (offline) {
                if (x == null || !x.getClass().isArray()) {
                    out.append(name);
                    for (int i : indexes) {
                        out.printf("[%d]", i);
                    }
                    out.append("=").append("" + x);
                    out.println();
                } else {
                    indexes = Arrays.copyOf(indexes, indexes.length + 1);
                    if (x instanceof byte[]) {
                        byte[] arr = (byte[]) x;
                        for (int i = 0; i < arr.length; i++) {
                            indexes[indexes.length - 1] = i;
                            debug(name, arr[i], indexes);
                        }
                    } else if (x instanceof short[]) {
                        short[] arr = (short[]) x;
                        for (int i = 0; i < arr.length; i++) {
                            indexes[indexes.length - 1] = i;
                            debug(name, arr[i], indexes);
                        }
                    } else if (x instanceof boolean[]) {
                        boolean[] arr = (boolean[]) x;
                        for (int i = 0; i < arr.length; i++) {
                            indexes[indexes.length - 1] = i;
                            debug(name, arr[i], indexes);
                        }
                    } else if (x instanceof char[]) {
                        char[] arr = (char[]) x;
                        for (int i = 0; i < arr.length; i++) {
                            indexes[indexes.length - 1] = i;
                            debug(name, arr[i], indexes);
                        }
                    } else if (x instanceof int[]) {
                        int[] arr = (int[]) x;
                        for (int i = 0; i < arr.length; i++) {
                            indexes[indexes.length - 1] = i;
                            debug(name, arr[i], indexes);
                        }
                    } else if (x instanceof float[]) {
                        float[] arr = (float[]) x;
                        for (int i = 0; i < arr.length; i++) {
                            indexes[indexes.length - 1] = i;
                            debug(name, arr[i], indexes);
                        }
                    } else if (x instanceof double[]) {
                        double[] arr = (double[]) x;
                        for (int i = 0; i < arr.length; i++) {
                            indexes[indexes.length - 1] = i;
                            debug(name, arr[i], indexes);
                        }
                    } else if (x instanceof long[]) {
                        long[] arr = (long[]) x;
                        for (int i = 0; i < arr.length; i++) {
                            indexes[indexes.length - 1] = i;
                            debug(name, arr[i], indexes);
                        }
                    } else {
                        Object[] arr = (Object[]) x;
                        for (int i = 0; i < arr.length; i++) {
                            indexes[indexes.length - 1] = i;
                            debug(name, arr[i], indexes);
                        }
                    }
                }
            }
            return this;
        }

    }

    static class IntegerList implements Cloneable {
        private int size;
        private int cap;
        private int[] data;
        private static final int[] EMPTY = new int[0];

        public IntegerList(int cap) {
            this.cap = cap;
            if (cap == 0) {
                data = EMPTY;
            } else {
                data = new int[cap];
            }
        }

        public void addAll(IntegerIterator iterator) {
            while (iterator.hasNext()) {
                add(iterator.next());
            }
        }

        public IntegerList(IntegerList list) {
            this.size = list.size;
            this.cap = list.cap;
            this.data = Arrays.copyOf(list.data, size);
        }

        public IntegerList() {
            this(0);
        }

        public void ensureSpace(int req) {
            if (req > cap) {
                while (cap < req) {
                    cap = Math.max(cap + 10, 2 * cap);
                }
                data = Arrays.copyOf(data, cap);
            }
        }

        private void checkRange(int i) {
            if (i < 0 || i >= size) {
                throw new ArrayIndexOutOfBoundsException();
            }
        }

        public int get(int i) {
            checkRange(i);
            return data[i];
        }

        public void add(int x) {
            ensureSpace(size + 1);
            data[size++] = x;
        }

        public void addAll(int[] x, int offset, int len) {
            ensureSpace(size + len);
            System.arraycopy(x, offset, data, size, len);
            size += len;
        }

        public void addAll(IntegerList list) {
            addAll(list.data, 0, list.size);
        }

        public int size() {
            return size;
        }

        public int[] toArray() {
            return Arrays.copyOf(data, size);
        }

        public String toString() {
            return Arrays.toString(toArray());
        }

        public boolean equals(Object obj) {
            if (!(obj instanceof IntegerList)) {
                return false;
            }
            IntegerList other = (IntegerList) obj;
            return SequenceUtils.equal(data, 0, size - 1, other.data, 0, other.size - 1);
        }

        public int hashCode() {
            int h = 1;
            for (int i = 0; i < size; i++) {
                h = h * 31 + Integer.hashCode(data[i]);
            }
            return h;
        }

        public IntegerList clone() {
            IntegerList ans = new IntegerList();
            ans.addAll(this);
            return ans;
        }

    }

    static interface IntegerDeque extends IntegerStack {
    }

    static class ConvexHullAssignProblem {
        public static double[] solve(double[] a) {
            int n = a.length;
            IntegerDequeImpl dq = new IntegerDequeImpl(n);
            for (int i = 0; i < n; i++) {
                while (dq.size() >= 2) {
                    int tail = dq.removeLast();
                    int tail2 = dq.peekLast();

                    if ((a[i] - a[tail]) / (i - tail) < (a[tail] - a[tail2]) / (tail - tail2)) {
                        dq.addLast(tail);
                        break;
                    }
                }

                dq.addLast(i);
            }

            IntegerList convexHull = new IntegerList(dq.size());
            convexHull.addAll(dq.iterator());

            double[] y = new double[n + 1];
            int left = 0;
            for (int i = 0; i < n; i++) {
                while (left + 1 < convexHull.size() && convexHull.get(left + 1) <= i) {
                    left++;
                }
                int last = convexHull.get(left);
                if (last == i) {
                    y[i] = a[i];
                } else {
                    int next = convexHull.get(left + 1);
                    y[i] = (double) (i - last) / (next - last) * (a[next] - a[last]) + a[last];
                }
            }

            return y;
        }

    }

    static class SequenceUtils {
        public static void swap(long[] data, int i, int j) {
            long tmp = data[i];
            data[i] = data[j];
            data[j] = tmp;
        }

        public static void rotate(long[] list, int l, int r, int to) {
            SequenceUtils.reverse(list, l, r);
            SequenceUtils.reverse(list, l, to - 1);
            SequenceUtils.reverse(list, to, r);
        }

        public static void reverse(long[] data, int l, int r) {
            while (l < r) {
                swap(data, l, r);
                l++;
                r--;
            }
        }

        public static boolean equal(int[] a, int al, int ar, int[] b, int bl, int br) {
            if ((ar - al) != (br - bl)) {
                return false;
            }
            for (int i = al, j = bl; i <= ar; i++, j++) {
                if (a[i] != b[j]) {
                    return false;
                }
            }
            return true;
        }

    }
}