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

namespace Atcoder
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] NK = Console.ReadLine().Split(' ').Select(int.Parse).ToArray();
            Hashtable h = new Hashtable();
            for (int i = 0; i < NK[0]; i++)
            {
                int[] ab = Console.ReadLine().Split(' ').Select(int.Parse).ToArray();
                if (h.Contains(ab[0]))
                {
                    long temp = long.Parse((h[ab[0]].ToString()));
                    temp += ab[1];
                    h[ab[0]] = temp;
                }
                else
                {
                    h[ab[0]] = ab[1];
                }
            }
            KeyValuePair<int, long>[] pairs = new KeyValuePair<int, long>[h.Count];

            int counter = 0;
            foreach (int key in h.Keys)
            {
                pairs[counter] = new KeyValuePair<int, long>(key, long.Parse(h[key].ToString()));
                counter++;
            }
            pairs = pairs.OrderBy(x => x.Key).ToArray();
            ;
            long answercount = NK[1];
            for (int i = 0; i < pairs.Length; i++)
            {
                answercount -= pairs[i].Value;
                if (answercount <= 0)
                {
                    Console.WriteLine(pairs[i].Key);
                    break;
                }
            }

            ;
        }
    }
}