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.Arrays;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;
public class Main {
	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);

		int N = sc.nextInt();
		int K = sc.nextInt();

		int[] a = new int[N];
		int[] b = new int[N];
		Map<Integer, Integer> map = new HashMap<Integer, Integer>();
		
		for (int i = 0; i < N; i++) {
			a[i] = sc.nextInt();
			b[i] = sc.nextInt();
		}

		for (int i = 0; i < N; i++) {
			int value = b[i];
			if (map.containsKey(a[i])) {
				value += (int)map.get(a[i]);
			}
			map.put(a[i], value);
		}
		
		Arrays.sort(a);
		
		for (int i = 0; i < a.length; i++) {
			
			K -= (int)map.get(a[i]);
			if (K <= 0) {
				System.out.println(a[i]);
				return;
			}
		}		
	}
}