Problem:
Score : 400 points

Problem Statement

There are N pieces of sushi. Each piece has two parameters: "kind of topping" t_i and "deliciousness" d_i.
You are choosing K among these N pieces to eat.
Your "satisfaction" here will be calculated as follows:

The satisfaction is the sum of the "base total deliciousness" and the "variety bonus".

The base total deliciousness is the sum of the deliciousness of the pieces you eat.

The variety bonus is x*x, where x is the number of different kinds of toppings of the pieces you eat.

You want to have as much satisfaction as possible.
Find this maximum satisfaction.

Constraints

1 \leq K \leq N \leq 10^5

1 \leq t_i \leq N

1 \leq d_i \leq 10^9

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N K
t_1 d_1
t_2 d_2
.
.
.
t_N d_N

Output

Print the maximum satisfaction that you can obtain.

Sample Input 1

5 3
1 9
1 7
2 6
2 5
3 1

Sample Output 1

26

If you eat Sushi 1,2 and 3:

The base total deliciousness is 9+7+6=22.

The variety bonus is 2*2=4.

Thus, your satisfaction will be 26, which is optimal.

Sample Input 2

7 4
1 1
2 1
3 1
4 6
4 5
4 5
4 5

Sample Output 2

25

It is optimal to eat Sushi 1,2,3 and 4.

Sample Input 3

6 5
5 1000000000
2 990000000
3 980000000
6 970000000
6 960000000
4 950000000

Sample Output 3

4900000016

Note that the output may not fit into a 32-bit integer type.

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Runtime Error)

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.math.BigDecimal;
import java.text.DecimalFormat;
import java.util.AbstractMap;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Deque;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.Set;
import java.util.Stack;
import java.util.TreeMap;
import java.util.TreeSet;

import static java.util.Comparator.*;

public class Main {

    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        MyInput in = new MyInput(inputStream);
        PrintWriter out = new PrintWriter(outputStream);

        Solver solver = new Solver(in, out);
        solver.solve();

        out.close();
    }

    // ======================================================================

    static class Solver {
    	MyInput in;
    	PrintWriter out;
        public Solver(MyInput in, PrintWriter out) {
        	this.in = in;
        	this.out = out;
        }
        
        // -----------------------------------------
        //
 		public void solve() {
			int N = ni();
			int K = ni();
			PP[] sushi = new PP[N];
			int t,d;
			for (int i = 0; i < N; i++) {
				t = ni();
				d = ni();
				sushi[i] = new PP(d, t);
			}
			// おいしさの大きい順に並べる
			Arrays.sort(sushi, Comparator.comparing(PP::getKey).reversed());
			
			MapCounter mc = new MapCounter();		// 計算に含まれる種類とその数
													// 計算に含まれていない、おいしさと種類（おいしさ順に並ぶ）
			PriorityQueue<PP> PQ = new PriorityQueue<PP>(comparing(PP::getKey, reverseOrder())); 
			// 初期の値を計算する
			long ans = 0;
			for (int i = 0; i < N; i++) {
				// おいしさの大きいものを　Ｋ個　足す
				if(i < K) {
					ans += sushi[i].getKey();
					mc.add(sushi[i].getVal());		//　種類の数をカウントする
				} else if(mc.getCount(sushi[i].getVal()) == 0){
					PQ.add(sushi[i]);				// 残りの寿司を突っ込む（まだ計算していない種類だけ）
				}
			}
			int kindCount = mc.getKeyCount();
			ans += kindCount * kindCount;
//			prn("1  ans = " + ans + " kindCount = " + kindCount);
			long wk = ans;
			PP p;
			for (int i = K - 1; i >= 0; i--) {
//				prn("sushi[" + i + "]  おいしさ = " + sushi[i].getKey() + "  種類 = " + sushi[i].getVal() + "  計算済みの個数 = " + mc.getCount(sushi[i].getVal()));
				if(mc.getCount(sushi[i].getVal()) > 1) {	// ２種類以上入っていたら、変更できる
					p = PQ.poll();
					if(mc.getCount(p.getVal()) == 0) {		// 残りの寿司がまだ計算していない種類ならば、計算する
						wk = wk - sushi[i].getKey() - (kindCount * kindCount) + p.getKey() + (kindCount + 1) * (kindCount + 1);
//						prn(" wk = " + wk + " <-- 前回値 - " + sushi[i].getKey() 
//								+ " - ((kindCount = " + kindCount + "}^2 = " + (kindCount * kindCount) + ") + "
//								+ p.getKey() + " + ((kindCount+1)^2 = " + ((kindCount + 1) * (kindCount + 1)) + ")");
						if(wk > ans) {
							ans = wk;
						}
						kindCount++;						// 種類を増やす
						mc.add(p.getVal());					// 計算に含まれる種類を追加する
						mc.sub(sushi[i].getVal());			// 減らした種類のカウントを減らす
					}
				}
			}
			prn(ans);
		}
        // -----------------------------------------
 		
        void prn(String s) {
        	out.println(s);
        }
        void prn(int i) {
        	out.println(i);
        }
        void prn(long i) {
        	out.println(i);
        }
        void prr(String s) {
        	out.print(s);
        }
        int ni() {
        	return in.nextInt();
        }
        long nl() {
        	return in.nextLong();
        }
        double nd() {
        	return in.nextDouble();
        }
        String ns() {
        	return in.nextString();
        }
        int[] ndi(int n) {
        	int[] ans = new int[n];
        	for(int i=0; i < n; i++) {
        		ans[i] = ni();
        	}
        	return ans;
        }
        long[] ndl(int n) {
        	long[] ans = new long[n];
        	for(int i=0; i < n; i++) {
        		ans[i] = nl();
        	}
        	return ans;
        }
        double[] ndd(int n) {
        	double[] ans = new double[n];
        	for(int i=0; i < n; i++) {
        		ans[i] = nd();
        	}
        	return ans;
        }
        String[] nds(int n) {
        	String[] ans = new String[n];
        	for(int i=0; i < n; i++) {
        		ans[i] = ns();
        	}
        	return ans;
        }
        int[][] nddi(int n, int m) {
        	int[][] ans = new int[n][m];
        	for(int i=0; i < n; i++) {
            	for(int j=0; j < m; j++) {
            		ans[i][j] = ni();
            	}
        	}
        	return ans;
        }
        long[][] nddl(int n, int m) {
        	long[][] ans = new long[n][m];
        	for(int i=0; i < n; i++) {
            	for(int j=0; j < m; j++) {
            		ans[i][j] = nl();
            	}
        	}
        	return ans;
        }
    }

    static class MapCounter {
    	private Map<Integer, Integer> map = new HashMap<Integer, Integer>();
    	public MapCounter() {}
    	public void add(int key) {
    		add(key, 1);
    	}
       	public void add(int key, int cnt) {
    		Integer val = map.get(key);
    		if(val == null) {
    			map.put(key, cnt);
    		} else {
    			map.put(key,  val + cnt);
    		}
    	}
    	public void sub(int key) {
    		sub(key, 1);
    	}
    	public void sub(int key, int cnt) {
    		Integer val = map.get(key);
    		if(val == null) {
    			map.put(key, -cnt);
    		} else {
    			map.put(key,  val - cnt);
    		}
    	}
    	public Integer getCountwithNull(int key) {
    		return map.get(key);
    	}
    	public int getCount(int key) {
    		Integer val = map.get(key);
    		if(val == null)		return 0;
    		else 				return val;
    	}
    	public Set<Integer> getKey() {
    		return map.keySet();
    	}
    	public int getKeyCount() {
    		return map.keySet().size();
    	}
    }
    static class PP{
    	public int key, val;
    	public PP(int key, int val) {
    		this.key = key;
    		this.val = val;
    	}
		public int getKey() {
			return key;
		}
		public void setKey(int key) {
			this.key = key;
		}
		public int getVal() {
			return val;
		}
		public void setVal(int val) {
			this.val = val;
		}
    }
    static class PPL {
    	public long key, val;
    	public PPL(long key, long val) {
    		this.key = key;
    		this.val = val;
    	}
		public long getKey() {
			return key;
		}
		public void setKey(long key) {
			this.key = key;
		}
		public long getVal() {
			return val;
		}
		public void setVal(long val) {
			this.val = val;
		}
    }
    static class PPDL {
    	public long key;
    	public long[] val;
    	public PPDL(long key, long[] val) {
    		this.key = key;
    		this.val = val;
    	}
		public long getKey() {
			return key;
		}
		public void setKey(long key) {
			this.key = key;
		}
		public long[] getVal() {
			return val;
		}
		public void setVal(long[] val) {
			this.val = val;
		}
		public void dump(PrintWriter out) {
			out.print("key = " + key + "  val ");
			for(int i=0; i < val.length; i++) {
				out.print("[" + val[i] + "] ");
			}
			out.println("");
		}
    }
    // HashMap のキーに使う
    static final class PPKEY{
    	private final int key, val;
    	public PPKEY(int key, int val) {
    		this.key = key;
    		this.val = val;
    	}
		public int getKey() {
			return key;
		}
		public int getVal() {
			return val;
		}
	    @Override
	    public boolean equals(Object obj) {
	        if (obj instanceof PPKEY) {
	        	PPKEY dest = (PPKEY) obj;
	            return this.key == dest.key && this.val == dest.val;
	        } else {
	            return false;
	        }
	    }
	    @Override
	    public int hashCode() {
	        return Objects.hash(key, val);
	    }
    }
    // HashMap のキーに使う
    static final class PPLKEY{
    	private final long key, val;
    	public PPLKEY(long key, long val) {
    		this.key = key;
    		this.val = val;
    	}
		public long getKey() {
			return key;
		}
		public long getVal() {
			return val;
		}
	    @Override
	    public boolean equals(Object obj) {
	        if (obj instanceof PPKEY) {
	        	PPKEY dest = (PPKEY) obj;
	            return this.key == dest.key && this.val == dest.val;
	        } else {
	            return false;
	        }
	    }
	    @Override
	    public int hashCode() {
	        return Objects.hash(key, val);
	    }
    }
    // グラフのリンクリスト
    static class Graph {
        private Map<Integer, List<Integer>> data = new HashMap<Integer, List<Integer>>();
        void add(int key, int value) {
        	List<Integer> list = data.get(key);
        	if(list == null) {
        		list = new ArrayList<Integer>();
        		data.put(key, list);
        	}
        	list.add(value);
        }
        List<Integer> get(int key) {
        	return data.get(key);
        }
        Set<Integer> keySet() {
        	return data.keySet();
        }
        boolean contains(int key, int value) {
        	List<Integer> list = data.get(key);
        	if(list == null)	return false;
        	else 				return list.contains(value);
        }
        void dump(PrintWriter out) {
        	for(int key : data.keySet()) {
        		out.print(key + " : ");
        		for(int val : data.get(key)) {
        			out.print(val + " ");
        		}
        		out.println("");
        	}
        }
    }
    // 重さを持ったグラフのリンクリスト
    static class GraphWith {
        private Map<Integer, List<PP>> data = new HashMap<Integer, List<PP>>();
        void add(int key, PP p) {
        	List<PP> list = data.get(key);
        	if(list == null) {
        		list = new ArrayList<PP>();
        		data.put(key, list);
        	}
        	list.add(p);
        }
        List<PP> get(int key) {
        	return data.get(key);
        }
        // グラフの存在チェック（重さは関係しない）
        boolean contains(int key, int value) {
        	List<PP> list = data.get(key);
        	if(list == null)	return false;
        	boolean ans = false;
        	for(PP p : list) {
        		if(p.getKey() == value) {
        			ans = true;
        			break;
        		}
        	}
        	return ans;
        }
    }
    // グラフのリンクリスト(Long)
    static class GraphLong {
        private Map<Long, List<Long>> G = new HashMap<Long, List<Long>>();
        void add(long key, long value) {
        	List<Long> list = G.get(key);
        	if(list == null) {
        		list = new ArrayList<Long>();
        		G.put(key, list);
        	}
        	list.add(value);
        }
        List<Long> get(long key) {
        	return G.get(key);
        }
    }
    // 重さを持ったグラフのリンクリスト(Long)
    static class GraphLongWith {
        private Map<Long, List<PPL>> G = new HashMap<Long, List<PPL>>();
        void add(long key, PPL p) {
        	List<PPL> list = G.get(key);
        	if(list == null) {
        		list = new ArrayList<PPL>();
        		G.put(key, list);
        	}
        	list.add(p);
        }
        List<PPL> get(long key) {
        	return G.get(key);
        }
    }

    // ======================================================================
    static class Pair<K, V> extends AbstractMap.SimpleEntry<K, V> {
        /** serialVersionUID. */
        private static final long serialVersionUID = 6411527075103472113L;

        public Pair(final K key, final V value) {
            super(key, value);
        }
     }
    static class MyInput {
        private final BufferedReader in;
        private static int pos;
        private static int readLen;
        private static final char[] buffer = new char[1024 * 8];
        private static char[] str = new char[500 * 8 * 2];
        private static boolean[] isDigit = new boolean[256];
        private static boolean[] isSpace = new boolean[256];
        private static boolean[] isLineSep = new boolean[256];

        static {
            for (int i = 0; i < 10; i++) {
                isDigit['0' + i] = true;
            }
            isDigit['-'] = true;
            isSpace[' '] = isSpace['\r'] = isSpace['\n'] = isSpace['\t'] = true;
            isLineSep['\r'] = isLineSep['\n'] = true;
        }

        public MyInput(InputStream is) {
            in = new BufferedReader(new InputStreamReader(is));
        }

        public int read() {
            if (pos >= readLen) {
                pos = 0;
                try {
                    readLen = in.read(buffer);
                } catch (IOException e) {
                    throw new RuntimeException();
                }
                if (readLen <= 0) {
                    throw new MyInput.EndOfFileRuntimeException();
                }
            }
            return buffer[pos++];
        }

        public int nextInt() {
            int len = 0;
            str[len++] = nextChar();
            len = reads(len, isSpace);
            int i = 0;
            int ret = 0;
            if (str[0] == '-') {
                i = 1;
            }
            for (; i < len; i++) ret = ret * 10 + str[i] - '0';
            if (str[0] == '-') {
                ret = -ret;
            }
            return ret;
        }

        public long nextLong() {
            int len = 0;
            str[len++] = nextChar();
            len = reads(len, isSpace);
            int i = 0;
            long ret = 0L;
            if (str[0] == '-') {
                i = 1;
            }
            for (; i < len; i++) ret = ret * 10 + str[i] - '0';
            if (str[0] == '-') {
                ret = -ret;
            }
            return ret;
        }

        public double nextDouble() {
            int len = 0;
            str[len++] = nextChar();
            len = reads(len, isSpace);
            int i = 0;
            double ret = 0;
            if (str[0] == '-') {
                i = 1;
            }
            int cnt = 0;
            for (; i < len; i++) {
            	if(str[i] == '.') {
            		cnt = 10;
            		continue;
            	}
            	if(cnt == 0) {
            		ret = ret * 10 + str[i] - '0';
            	} else {
            		ret = ret + ((double)(str[i] - '0') / cnt);
            		cnt *= 10;
            	}
            }
            if (str[0] == '-') {
                ret = -ret;
            }
            return ret;
        }

       public String nextString() {
        	String ret = new String(nextDChar()).trim();
            return ret;
        }

        public char[] nextDChar() {
            int len = 0;
            len = reads(len, isSpace);
            char[] ret = new char[len + 1];
            for (int i=0; i < len; i++)		ret[i] = str[i];
            ret[len] = 0x00;
            return ret;
        }

        public char nextChar() {
            while (true) {
                final int c = read();
                if (!isSpace[c]) {
                    return (char) c;
                }
            }
        }

        int reads(int len, boolean[] accept) {
            try {
                while (true) {
                    final int c = read();
                    if (accept[c]) {
                        break;
                    }
                    if (str.length == len) {
                        char[] rep = new char[str.length * 3 / 2];
                        System.arraycopy(str, 0, rep, 0, str.length);
                        str = rep;
                    }
                    str[len++] = (char) c;
                }
            } catch (MyInput.EndOfFileRuntimeException e) {
            }
            return len;
        }

        static class EndOfFileRuntimeException extends RuntimeException {
        }
    }
}