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 Java7 (OpenJDK 1.7.0) (judge verdict: Runtime Error)

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Scanner;
import java.util.SortedSet;
import java.util.TreeSet;

public class Main{
	 
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		long k = scan.nextInt();
 
		SortedSet<Long> set = new TreeSet<>();
		Map<Long, Long> map = new HashMap<>();
		for(int i = 0; i < n; i++){
			long a = scan.nextInt();
			long b = scan.nextInt();
			set.add(a);
			if(map.containsKey(a)){
				map.put(a, map.get(a) + b);
			}else{
				map.put(a, b);
			}
		}
 
		for(Iterator it = set.iterator();;){
			long num = (long) it.next();
			k -= map.get(num);
			if(k <= 0){
				System.out.println(num);
				break;
			}
		}
 
	}
 
}