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# (.NET Core 3.1.201) (judge verdict: Runtime Error)

using System;
using System.Linq;

namespace ConsoleApp3
{
    internal class Class2
    {
        private static void Main(string[] args)
        {
            var nk = Console.ReadLine().Split(" ").Select(int.Parse).ToArray();
            var n = nk[0];
            var k = nk[1];


            var result = Enumerable.Range(0, n)
                .SelectMany(_ =>
                {
                    var ab = Console.ReadLine().Split(" ").Select(int.Parse).ToArray();

                    return Enumerable.Repeat(ab[0], ab[1]);
                })
                .OrderBy(x => x)
                .Skip(k - 1)
                .First();

            Console.WriteLine(result);
        }
    }
}