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: Accepted)

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

namespace c
{
    class Program
    {
        static void Main(string[] args)
        {
            var _ = Console.ReadLine().Split();
            var n = long.Parse(_[0]);
            var k = long.Parse(_[1]);

            var d = new Dictionary<long,long>();
            for(var i = 0; i < n; i++){
                var __ = Console.ReadLine().Split();
                var a = long.Parse(__[0]);
                var b = long.Parse(__[1]);

                if(d.ContainsKey(a)){
                    d[a] += b;
                }else{
                    d.Add(a,b);
                }
            }

            var count = 0L;
            foreach(var item in d.OrderBy(i => i.Key)){
                count += item.Value;
                if(count >= k){
                    Console.WriteLine(item.Key);
                    break;
                }
            }

        }
    }
}