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.Scanner;
import java.util.Arrays;
import java.util.TreeMap;
import java.util.Iterator;

public class Main {
	public static void main(String[] args) {
		BigArray bg = new BigArray();
		bg.exec();
	}
}

class BigArray {
	static long n;
	static long k;
	static TreeMap<Long, Long> map = new TreeMap<Long, Long>();

	public BigArray() {
		Scanner cin = new Scanner(System.in);
		this.n = cin.nextLong();
		this.k = cin.nextLong();
		for (int i = 0; i < n; i++) {
			long a = cin.nextLong();
			long b = cin.nextLong();
			if (map.containsKey(a)) {
				map.put(a, map.get(a) + b);
			} else {
				map.put(a, b);
			}
		}
	}

	void exec(){
		long cur_i = 0;
		for(long key : map.keySet()) {
			cur_i += map.get(key);
			if(cur_i >= k){
				System.out.println(key);
				return;
			}
		}
	}
}