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 Java8 (OpenJDK 1.8.0) (judge verdict: Time Limit Exceeded)

import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;

public class Main {
	public static void main(String[] args)  {
		Scanner sc = new Scanner((System.in));
		int n = sc.nextInt();
		long k = sc.nextLong();
		ArrayList<Integer> al = new ArrayList<Integer>();
		int tmpnum = 0;
		int tmpcount = 0;
		for(int i = 0; i < n; i++) {
			tmpnum = sc.nextInt();
			tmpcount = sc.nextInt();
			for(int j = 0; j < tmpcount; j++) {
				al.add(tmpnum);
			}
		}
		Collections.sort(al);

		System.out.println(al.get((int) (k-1)));
	}
}