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

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

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

            var tupleList = new List<Tuple<int, int>>();

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

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

                tupleList.Add(new Tuple<int, int>(a[i], b[i]));
            }

            tupleList.Sort((p, q) => p.Item1.CompareTo(q.Item1));

            int remain = K;
            int index = 0;

            while (remain > 0) {
                if (remain - tupleList[index].Item2 <= 0) {
                    Console.WriteLine(tupleList[index].Item1);
                    return;
                }

                remain -= tupleList[index].Item2;
                index++;
                if (remain < 0) {
                    break;
                }
            }

        }
    }
}