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;

namespace AtCoder {
	class Program {
		public static void Main() {
			long[] input = new long[2];
			input = Console.ReadLine().Split(' ').Select(long.Parse).ToArray();
			long n = input[0];
			long k = input[1];
			long[] a = new long[n];
			long[] b = new long[n];
			for (long i = 0; i < n; i++) {
				input = Console.ReadLine().Split(' ').Select(long.Parse).ToArray();
				a[i] = input[0];
				b[i] = input[1];
			}
			Array.Sort(a, b);
			long j = 0;
			long c = 0;
			while (c + b[j] < k) {
				c += b[j];
				j++;
			}
			Console.WriteLine(a[j]);
		}
	}
}