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.*;

public class Main {
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		long k = sc.nextLong();
		long total = 0;
		Pair[] pairs = new Pair[n];
		for (int i = 0; i < n; i++) {
		    pairs[i] = new Pair(sc.nextInt(), sc.nextInt());
		}
		Arrays.sort(pairs);
		for (int i = 0; i < n; i++) {
		    total += pairs[i].b;
		    if (total >= k) {
		        System.out.println(pairs[i].a);
		        return;
		    }
		}
	}
	
	static class Pair implements Comparable<Pair> {
	    int a;
	    int b;
	    public Pair(int a, int b) {
	        this.a = a;
	        this.b = b;
	    }
	    
	    public int compareTo(Pair another) {
	        return a - another.a;
	    }
	}
}