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.Linq;
using System.Collections.Generic;

namespace Algorithm
{
    class Program
    {
        static void Main(string[] args)
        {
            var l = Console.ReadLine().Split().Select(long.Parse).ToArray();
            long N = l[0], K = l[1];

            var dict = new Dictionary<int, long>();

            for (var i = 0; i < N; i++)
            {
                var tmp = Console.ReadLine().Split().Select(int.Parse).ToArray();
                if (dict.ContainsKey(tmp[0]))
                    dict[tmp[0]] += tmp[1];
                else
                    dict[tmp[0]] = tmp[1];
            }

            var total = 0L;
            foreach (var d in dict.OrderBy(z => z.Key))
            {
                total += d.Value;
                if (K <= total)
                {
                    Console.WriteLine(d.Key);
                    return;
                }
            }
            
        }
    }
}