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

namespace ABC_C
{
    class C061
    {
        static void Main(string[] args)
        {
            string[] s1 = Console.ReadLine().Split(' ');
            int N = int.Parse(s1[0]);
            int K = int.Parse(s1[1]);

            SortedDictionary<int, int> dic = new SortedDictionary<int, int>();
            List<int> list = new List<int>();
            for (int i = 0; i < N; i++)
            {
                string[] s = Console.ReadLine().Split(' ');
                int a = int.Parse(s[0]);
                int b = int.Parse(s[1]);

                if (!dic.ContainsKey(a)) dic.Add(a, 0);
                dic[a] += b;
            }

            long counter = 0;
            int index = 0;
            while (true)
            {
                counter += dic.Values.ToList()[index];
                if (counter <= K) break;
                index++;
            }
            int x = dic.Keys.ToList()[index];
            Console.WriteLine(x);

        }
    }
}