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 ABC61_C
{
    class Program
    {
        static void Main(string[] args)
        {
            var s = Console.ReadLine().Split();
            int n = int.Parse(s[0]);
            int k = int.Parse(s[1]);
            var a = new int[n];
            var b = new SortedDictionary<int, long>();
            for (int i = 0; i < n; i++)
            {

                var t = Console.ReadLine().Split().Select(int.Parse).ToArray();

                a[i] = t[0];
                if (!b.ContainsKey(a[i])) b[a[i]] = 0;
                b[a[i]] += t[1];

            }
            var ke = b.OrderBy(x => x.Key);
            long count = 0;
            foreach (var item in ke)
            {
                count += item.Value;
                if (count >= k)
                {

                    Console.WriteLine(item.Key);
                    return;
                }
            }

        }
    }
}