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 System.Text;
using System.Threading.Tasks;

namespace ConsoleApp107 {
    class Program {
        static void Main(string[] args) {
            var st = Console.ReadLine().Split().Select(long.Parse).ToArray();

            long N = st[0];
            long K = st[1];

            var a = new long[N];
            var b = new long[N];

            var ans = new long[100010];

            for (int i = 0; i < N; i++) {
                var x = Console.ReadLine().Split().Select(long.Parse).ToArray();

                a[i] = x[0];
                b[i] = x[1];

                ans[a[i]] += b[i];
            }



            for (int i = 0; i < 100010; i++) {
                K -= ans[i];

                if (K <= 0) {
                    Console.WriteLine(i);
                    break;
                }
            }

                

        }
    }
}