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.Collections.Generic;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] str0 = Console.ReadLine().Split(' ');
            int N = int.Parse(str0[0]);
            int K = int.Parse(str0[1]);

            int[] arrA = new int[N];
            int[] arrB = new int[N];
            List<int> lstReault = new List<int>();

            for(int i=0; i<N; i++)
            {
                string[] str = Console.ReadLine().Split(' ');
                if (str.Length < 2) break;

                int a = int.Parse(str[0]);
                int b = int.Parse(str[1]);

                for(int j=0; j<b; j++)
                {
                    lstReault.Add(a);
                }
            }

            //int temp;
            //for (int i = 0; i < lstReault.Count - 1; i++)
            //{
            //    for (int j = lstReault.Count-1; j > i; j--)
            //    {
            //        if (lstReault[j] < lstReault[i])
            //        {
            //            temp = lstReault[i];
            //            lstReault[i] = lstReault[j];
            //            lstReault[j] = temp;
            //        }
            //    }
            //}
            lstReault.Sort();
            Console.WriteLine(lstReault[K-1]);

            Console.ReadKey();
        }
    }
}