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: Time Limit Exceeded)

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

class Program
{
    static void Main()
    {
        var nk = Array.ConvertAll(Console.ReadLine().Split(), long.Parse);
        var list = new List<int[]>();
        var dic = new Dictionary<int, long>();
        for (int i = 0; i < nk[0]; i++)
        {
            list.Add(Array.ConvertAll(Console.ReadLine().Split(), int.Parse));
            dic[list[i][0]] = 0;
        }
        for (int i = 0; i < nk[0]; i++) dic[list[i][0]] += list[i][1];
        dic = dic.OrderBy(x => x.Key).ToDictionary(x => x.Key, x => x.Value);
        for (int i = 0; i < dic.Count(); i++)
        {
            nk[1] -= dic.ElementAt(i).Value;
            if (nk[1] <= 0)
            {
                Console.WriteLine(dic.ElementAt(i).Key);
                break;
            }
        }
    }
}