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;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ABC061C
{
    class Program
    {
        static void Main(string[] args)
        {
            var list = new List<long>();
            string []str = Console.ReadLine().Split();
            var N = long.Parse(str[0]);
            var K = int.Parse(str[1]);
            for(var i = 0; i < N; i++)
            {
                str = Console.ReadLine().Split();
                var a = long.Parse(str[0]);
                var b = int.Parse(str[1]);
                if(list.Count < K)
                {
                    for (int j = 0; j < b; j++)
                    {
                        list.Add(a);
                    }

                    list.Sort();
                }
                else if (list.Count > K&&a<list.Last())
                {
                    for (int j = 0; j < b; j++)
                    {
                        list.Add(a);
                    }
                    list.RemoveRange(K + 1, b);

                    list.Sort();
                }
            }
            Console.WriteLine(list[K - 1]);
        }
    }
}