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.Linq;

namespace ABC061_C
{
    class Program
    {
        static void Main(string[] args)
        {
            var NK = Console.ReadLine().Split().Select(int.Parse).ToArray();
            var N = NK[0];
            var K = NK[1];

            var m = new Model[N];
            var s = new long[N];
            for (int i = 0; i < N; i++)
            {
                m[i] = new Model();
                var ab = Console.ReadLine().Split().Select(int.Parse).ToArray();
                m[i].A = ab[0];
                m[i].B = ab[1];
            }

            m = m.OrderBy(x => x.A).ToArray();

            var ans = 0;
            for (int i = 0; i < N; i++)
            {
                s[i] = (i >= 1 ? s[i - 1] : 0) + m[i].B;
                if (s[i] >= K)
                {
                    ans = m[i].A;
                    break;
                }
            }

            Console.WriteLine(ans);
        }

        public class Model
        {
            public int A { get; set; }
            public int B { get; set; }
        }
    }
}