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: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using System.IO;
using System.Text;
using static System.Console;
using static System.Math;

namespace CP
{
    class Atria
    {
        static void Main(string[] args)
        {
            long[] nk = ReadLine().Split(' ').Select(long.Parse).ToArray();
            var sortedDic = new SortedDictionary<int,long>();
            for (int i = 0; i < nk[0]; i++)
            {
                long[] s = ReadLine().Split(' ').Select(long.Parse).ToArray();
                try
                {
                    sortedDic.Add((int)s[0],s[1]);
                }
                catch (Exception)
                {
                    sortedDic[(int)s[0]] += s[1];
                }
            }
            long tmp = 0;
            int j = 0;
            foreach (var item in sortedDic)
            {
                j++;
                tmp += item.Value;
                if (tmp >= nk[1])
                {
                    WriteLine(item.Key);
                    return;
                }
            }
        }
    }
}