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;
using static System.Math;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            var array = Console.ReadLine().Split();
            int n = int.Parse(array[0]);
            long k = long.Parse(array[1]) - 1;

            var blocks = (from _ in Enumerable.Repeat(0, n)
                          let cols = Console.ReadLine().Split().Select(int.Parse).ToArray()
                          let block = new { Value = cols[0], Count = cols[1] }
                          orderby block.Value
                          select block).ToArray();

            long current = 0;
            foreach (var block in blocks)
            {
                if (current <= k && k < current + block.Count)
                {
                    Console.WriteLine(block.Value);
                    break;
                }

                current += block.Count;
            }
        }
    }
}