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.Linq;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        var line = Console.ReadLine().Split(' ').Select(x => Int64.Parse(x)).ToArray();
        var N = line[0];
        var K = line[1];
        var list = new List<long[]>();
        for (var i=0;i<N;++i)
        {
            var ab = Console.ReadLine().Split(' ').Select(x => Int64.Parse(x)).ToArray();
            list.Add(new long[] { ab[0],ab[1]});
        }
        var orderList=list.OrderBy(x => x[0]);
        var ans = 0L;
        foreach (var l in orderList)
        {
            K -= l[1];
            if (K <= 0)
            {
                ans = l[0];
                break;
            }
        }
        Console.WriteLine(ans);
    }
}