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: Accepted)

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

public class Main {
	public static void main(String[]args) {
		try(Scanner scan = new Scanner(System.in)){
			
			int N = scan.nextInt();
			long K = scan.nextLong();
			long[]a = new long[N];
			long[]b = new long[N];
			Map<Long,Long>map = new TreeMap<Long,Long>();
			for(int i = 0;i<N;i++) {
				a[i] = scan.nextLong();
				b[i] = scan.nextLong();
				if(map.containsKey(a[i])) {
					map.put(a[i], map.get(a[i])+b[i]);
				}else {
					map.put(a[i], b[i]);
				}
			}
			
			long ans = 0;
			for(Long key:map.keySet()) {
				K-=map.get(key);
				if(K<=0) {
					ans = key;
					break;
				}else if(K>0){
					ans = key;
				}
				
			}
			
			
			System.out.println(ans);
			
			
			
			
			
		}
		
		
	}
		

}