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)

//#pragma warning disable

using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Text;

public class Test
{
    public static void Main()
    {
        var line1 = Console.ReadLine().Split(' ').Select(long.Parse).ToArray();
        var N = line1[0];
        var K = line1[1];

        var a = new long[N];
        var b = new long[N];

        for (var i = 0; i < N; i++)
        {
            var line2 = Console.ReadLine().Split(' ').Select(long.Parse).ToArray();
            a[i] = line2[0];
            b[i] = line2[1];
        }

        var sorted = Enumerable.Range(0, (int)N).Select(i => Tuple.Create(a[i], b[i])).OrderBy(x => x.Item1).ToArray();

        long sum = 0;

        foreach (var tuple in sorted)
        {
            sum += tuple.Item2;

            if (sum >= K)
            {
                Console.WriteLine(tuple.Item1);
                return;
            }
        }
    }
}