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.Linq;

class Program
{
    static void Main(string[] args)
    {
        string[] s = Console.ReadLine().Split(' ');
        int N = int.Parse(s[0]);
        ulong K = ulong.Parse(s[1]);
        var array = Enumerable.Repeat((ulong)0, AMAX + 1).ToArray();
        for (int i = 0; i < N; i++)
        {
            string[] ss = Console.ReadLine().Split(' ');
            int a = int.Parse(ss[0]);
            int b = int.Parse(ss[1]);
            array[a] += (ulong)b;
        }
        ulong itemNum = 0;
        for (int i = 1; i <= N; i++)
        {
            itemNum += array[i];
            if (itemNum >= K)
            {
                Console.WriteLine(i);
                return;
            }
        }
    }
  	public const int AMAX = 100000;
}