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

class AtCoder
{
    static AtCoder atCoder;
    public static void Main()
    {
        atCoder = new AtCoder();
        atCoder.Run();
    }

    static void staticMethod()
    {
        atCoder.Run();
    }

    void Run()
    {
        var line = System.Console.ReadLine();
        string[] inputs = line.Split();
        int insertNum = int.Parse(inputs[0]);
        int getNum = int.Parse(inputs[1]);

        SortedList<int, int> entireList = new SortedList<int, int>();

        int number = 0;
        int repeat = 0;
        for(int i = 0; i < insertNum; i++)
        {
            line = System.Console.ReadLine();
            inputs = line.Split();
            number = int.Parse(inputs[0]);
            repeat = int.Parse(inputs[1]);

            if (!entireList.ContainsKey(number))
            {
                entireList.Add(number, 0);
            }

            int beforeValue=0;
            beforeValue = entireList.ElementAt(entireList.IndexOfKey(number)).Value;
            entireList.Remove(number);
            entireList.Add(number, beforeValue + repeat);
        }

        System.Console.WriteLine(GetByIndex(getNum, entireList));
    }

    private int GetByIndex(int index, SortedList<int, int> target)
    {
        int counter = index;        

        foreach(KeyValuePair<int, int> pair in target)
        {
            counter -= pair.Value;
            if(counter <= 0)
            {
                return pair.Key;
            }
        }

        return -1;
    }
}