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 AtCoder_Cs
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] line = Console.ReadLine().Trim().Split(' ').Select(int.Parse).ToArray();
            int N = line[0];
            int K = line[1];
            List<string> list = new List<string>();

            for (int i = 0;i < N; ++i)
            {
                string[] line2 = Console.ReadLine().Trim().Split(' ');
                for (int j = 0;j < int.Parse(line2[1]); ++j)
                {
                    list.Add(line2[0]);
                }
            }

            var ans = list.OrderBy(s => s).Select(s => s);
            int cnt = 1;
            string result = string.Empty;
            foreach (var item in ans)
            {
                if (cnt == K)
                {
                    result = item.ToString();
                    break;
                }
                ++cnt;
            }
            Console.WriteLine($"{result}");
            Console.ReadLine();
        }
    }
}