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: Runtime Error)

using System;
using System.Text;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Threading.Tasks;

class Solve
{
	const int mod = 1000000007;
	static void Main(string[] args)
	{
		var input = Console.ReadLine().Split().Select(int.Parse).ToArray();
		int N = input[0];
		int K = input[1];
		List<Tuple<int, int>> ab = new List<Tuple<int, int>>();

        for(var i = 0; i < N; i++)
		{
			var p = Console.ReadLine().Split().Select(int.Parse).ToArray();
			ab.Add(new Tuple<int, int>(p[0], p[1]));
		}
		ab.Sort();
		long ans = 0;
		long sum = 0;
        for(var i = 0; i < N; i++)
		{
			sum += ab[i].Item2;
			if (sum >= K)
			{
				ans = ab[i].Item1;
				break;
			}
		}
		Console.WriteLine(ans);


	}
}