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;

namespace ABC061C
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] bufs = Console.ReadLine().Split(' ');
            int N = Int32.Parse(bufs[0]);
            long K = Int64.Parse(bufs[1]);

            int[] a = new int[N];
            int[] b = new int[N];

            for (int i = 0; i < N; i++)
            {
                bufs = Console.ReadLine().Split(' ');
                a[i] = Int32.Parse(bufs[0]);
                b[i] = Int32.Parse(bufs[1]);
            }

            Array.Sort(a, b);
            int idx = -1;
            while (K > 0)
            {
                idx++;
                K -= b[idx];
            }

            Console.WriteLine(a[idx]);
        }
    }
}