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.Text;
using System.Numerics;
using System.IO;

namespace SolutionCS
{
    class Program
    {
        class Entity : IComparable<Entity>
        {
            public int number;
            public int count;

            public int CompareTo(Entity e)
            {
                return number.CompareTo(e.number);
            }
        }


        static void Main(string[] args)
        {
            string[] s = Console.ReadLine().Split(' ');
            int N = int.Parse(s[0]);
            long M = long.Parse(s[1]);

            List<Entity> l = new List<Entity>();
            for (int i = 0; i < N; i++)
            {
                s = Console.ReadLine().Split(' ');

                Entity e = new Entity();
                e.number = int.Parse(s[0]);
                e.count = int.Parse(s[1]);

                l.Add(e);
            }

            l.Sort();

            long total = 0;

            for (int i = 0; i < l.Count; i++)
            {
                total += l[i].count;

                if (M <= total)
                {
                    Console.WriteLine(l[i].number);
                    break;
                }

            }
        }
    }
}