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: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;

namespace ConsoleApp11
{
    class Class40
    {
        static void Main()
        {
            var I = Console.ReadLine().Split().Select(long.Parse).ToArray();
            var N = I[0];
            var K = I[1];
            Dictionary<long, long> Table = new Dictionary<long, long>();
            for(int i = 0; i < N; i++)
            {
                var read = Console.ReadLine().Split().Select(long.Parse).ToArray();
                if (Table.Keys.Contains(read[0]))
                {
                    Table[read[0]] += read[1];
                }
                else
                {
                    Table[read[0]] = read[1];
                }
            }
            long sum = 0;
            foreach(long L in Table.Keys)
            {
                sum += Table[L];
                if (sum >= K)
                {
                    Console.WriteLine(L);
                    return;
                }
            }
        }
    }
}