Problem:
Score : 300 points

Problem Statement

There is an empty array.
The following N operations will be performed to insert integers into the array.
In the i-th operation (1≤i≤N), b_i copies of an integer a_i are inserted into the array.
Find the K-th smallest integer in the array after the N operations.
For example, the 4-th smallest integer in the array \{1,2,2,3,3,3\} is 3.

Constraints

1≤N≤10^5

1≤a_i,b_i≤10^5

1≤K≤b_1…+…b_n

All input values are integers.

Input

Input is given from Standard Input in the following format:

N K
a_1 b_1
:
a_N b_N

Output

Print the K-th smallest integer in the array after the N operations.

Sample Input 1

3 4
1 1
2 2
3 3

Sample Output 1

3

The resulting array is the same as the one in the problem statement.

Sample Input 2

10 500000
1 100000
1 100000
1 100000
1 100000
1 100000
100000 100000
100000 100000
100000 100000
100000 100000
100000 100000

Sample Output 2

1

Solution in C# (Mono 4.6.2.0) (judge verdict: Runtime Error)

using System;
using System.Collections.Generic;

namespace MyProgram{
    class AtCoder{
        static void Main(){
            int[] input0 = Array.ConvertAll(Console.ReadLine().Split(' '),int.Parse);
            int N = input0[0];
            int K = input0[1];
            int[] a = new int[N];
            int[] b = new int[N];
            for(var i=0;i<N;i++){
                int[] input = Array.ConvertAll(Console.ReadLine().Split(' '),int.Parse);
                a[i] = input[0];
                b[i] = input[1];
            }
            var dict = new Dictionary<int,long>();
            for(var i=0;i<N;i++){
                if(!dict.ContainsKey(a[i]))dict[a[i]] = b[i];
                else dict[a[i]]+=b[i];
            }
            Array.Sort(a);
            int temp = -1;
            long count=0;
            for(var i=0;i<N;i++){
                if(temp != a[i])count+=dict[a[i]];
                temp = a[i];
                if(count >=K){
                    Console.WriteLine(a[i]);
                    break;
                }
            }
        }  
    } 
}