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;

namespace ABC061
{
    class Program
    {
        static void Main(string[] args)
        {
            var s = Console.ReadLine().Split(' ');
            var n = int.Parse(s[0]);
            var k = int.Parse(s[1]);

            var arr = new MyArray(k);

            for (var i = 0; i < n; i++)
            {
                s = Console.ReadLine().Split(' ');
                var a = int.Parse(s[0]);
                var b = int.Parse(s[1]);
                arr.Add(a, b);
            }

            Console.WriteLine(arr.GetLast());
        }
    }

    struct MyArray
    {
        private readonly int[] _arr;
        private int _count;

        public MyArray(int k)
        {
            _arr = new int[k];
            _count = 0;
        }

        public void Add(int a, int b)
        {
            var insertIndex = 0;
            if (_count > 0)
            {
                if (_count > 0 && _arr[_count - 1] <= a)
                {
                    if (_count == _arr.Length) return;
                    insertIndex = _count;
                }
                else
                {
                    for (var i = _count - 1; i >= 0; i--)
                    {
                        if (_arr[i] <= a)
                        {
                            insertIndex = i + 1;
                            break;
                        }
                    }
                }
            }

            var copyDest = insertIndex + b;
            if (copyDest < _arr.Length)
            {
                Array.Copy(_arr, insertIndex, _arr, copyDest, _arr.Length - copyDest);
            }

            for (var i = 0; i < b; i++)
            {
                if (insertIndex >= _arr.Length) break;

                _arr[insertIndex++] = a;
            }

            _count = Math.Min(_count + b, _arr.Length);
        }

        public int GetLast()
        {
            return _arr[_arr.Length - 1];
        }
    }
}