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;

class Program {

    static void Main() {
        string input = Console.ReadLine();
        int operation_count = int.Parse(input.Split(' ')[0]);
        int answer_index    = int.Parse(input.Split(' ')[1]);

        List<int> target_nums   = new List<int>();
        List<int> repeat_counts = new List<int>();

        for (int i = 0; i < operation_count; i++) {
            input = Console.ReadLine();
            int target_num   = int.Parse(input.Split(' ')[0]);
            int repeat_count = int.Parse(input.Split(' ')[1]);

            int insert_index;
            try {
                int insert_num = target_nums.Where(n => n >= target_num).Min();
                insert_index = target_nums.LastIndexOf(insert_num);
            } catch (InvalidOperationException e) {
                insert_index = target_nums.Count;
            }

            target_nums.Insert(insert_index, target_num);
            repeat_counts.Insert(insert_index, repeat_count);

        }

        int sum = 0;
        for(int i = 0; i < repeat_counts.Count; i++) {
            sum += repeat_counts[i];
            if (sum >= answer_index) {
                Console.WriteLine(target_nums[i]);
                return;
            }
        }
    }
}