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;

namespace WelcomeAtcordet
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] input = Console.ReadLine().Split(' ');
            int N = int.Parse(input[0]);
            int K = int.Parse(input[1]);
            int[] num = new int[N];
            int[] multi_num = new int[N];

            for (int i = 0; i < N; i++)
            {
                string[] input2 = Console.ReadLine().Split(' ');
                num[i] = int.Parse(input2[0]);
                multi_num[i] = int.Parse(input2[1]);
            }
            int[] sort_num = num;
            Array.Sort(sort_num);

            int sum = 0;
            int min = sort_num[0];
            int index = 0;

            while (sum < K)
            {
                index = Array.IndexOf(num, min);
                while (index >= 0)
                {
                    sum += multi_num[index];
                    if (sum >= K)
                    {
                        break;
                    }
                    index = Array.IndexOf(num, min, index + 1);
                }
                min = Array.Find(sort_num, n => n > min);
            }

            Console.WriteLine(num[index]);
        }
    }
}