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: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;

namespace ABC061_C
{
    class Program
    {
        static void Main(string[] args)
        {
            var max = 100000;
            var ar = new long[max+1];
            var NK = Console.ReadLine().Split().Select(long.Parse).ToArray();
            var N = NK[0];
            var K = NK[1];

            for (int i = 0; i < N; i++)
            {
                var tempAB = Console.ReadLine().Split().Select(long.Parse).ToArray();
                var a = tempAB[0];
                var b = tempAB[1];
                ar[a] += b;
            }

            var ans = 0;
            var n = 0;
            for (int i = 1; i < max; i++)
            {
                if (K<=ar[i])
                {
                    ans = i;
                    break;
                }
                K -= ar[i];
            }
            Console.WriteLine(ans);
        }
    }
}