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.*;
import static java.lang.Math.*;

public class Main {
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		
		// 入力
		int n = sc.nextInt();
		int k = sc.nextInt();
		int[][] ab = new int[n][2];
		for(int i = 0; i < n; i++){
		    int a = sc.nextInt();
		    int b = sc.nextInt();
		    ab[i][0] = a;
		    ab[i][1] = b;
		}
		Arrays.sort(ab, (s, t) -> Integer.compare(s[0], t[0]));
		
		// 計算
		int result = 0;
		for(int i = 0; i < n; i++){
		    k -= ab[i][1];
		    if(k <= 0){
		        result = ab[i][0];
		        break;
		    }
		}
		
		// 出力
		System.out.println(result);
	}
}