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: Runtime Error)

import java.util.Map.Entry;
import java.util.Scanner;
import java.util.SortedMap;
import java.util.TreeMap;

public class Main {

	public static void main(String[] args) {
		Scanner reader = new Scanner(System.in);
		int N = reader.nextInt();
		int K = reader.nextInt();
		long ans = 0;
		SortedMap<Long, Long> map = new TreeMap<Long, Long>();

		for (int i = 0 ; i < N; i++) {
			long key = reader.nextLong();
			long value = reader.nextLong();
			if (map.containsKey(key)) {
				value += map.get(key);
			}
			map.put(key, value);
		}

		for (Entry<Long, Long> entry : map.entrySet()) {
			K -= entry.getValue();
			if (K <= 0) {
				ans = entry.getKey();
				break;
			}
		}

		System.out.println(ans);
		reader.close();

	}
}