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

class Program
{
    private static readonly Scanner sc = new Scanner();
    static void Main(string[] args)
    {
        int n = sc.Int;
        int k = sc.Int;

        int[] cnt = new int[100001];

        for (int i = 0; i < n; i++)
        {
            int a = sc.Int;
            int b = sc.Int;

            cnt[a] += b;
        }

        int j = 0;
        int c = 0;
        while (c < k)
            c += cnt[j++];
        
        Console.WriteLine(j - 1);
    }
}

class Scanner
{
    private string[] _str = new string[0];
    private int _i;

    public string Str
    {
        get
        {
            if (_i >= _str.Length)
            {
                _str = Console.ReadLine().Split(' ');
                _i = 0;
            }
            return _str[_i++];
        }
    }

    public int Int { get { return int.Parse(Str); } }
    public long Long { get { return long.Parse(Str); } }
    public double Double { get { return double.Parse(Str); } }
}