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 Java (OpenJDK 11.0.6) (judge verdict: Accepted)

import java.util.*;
// warm-up
public class Main {

	static void solve() {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt(), n=N;
		double K = sc.nextDouble(), t=0;
		Map<Double, Double> m = new HashMap<Double, Double>();
		Queue<Double> minQueue = new PriorityQueue<Double>();
		while (n-->0) {
			double b = sc.nextDouble(), c = sc.nextDouble();
			if (!m.containsKey(b)) minQueue.add(b);
			m.put(b,m.get(b)==null ? c : m.get(b)+c);
		}
		while (!minQueue.isEmpty()) {
			double k = minQueue.poll();
			if (t==K||t+m.get(k)>=K) {
				System.out.println((int)k); System.exit(0);				
			}
			t+=m.get(k);
		}
		sc.close();		
	}

	public static void main(String args[]) {
		solve();
	}

}