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.Arrays;
import java.util.Comparator;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner scan = new Scanner(System.in);
		int N=scan.nextInt();
		String s=scan.next();
		long K =Long.parseLong(s);

		int[][] ab = new int[N][2];
		for(int i=0;i<N;i++){
			ab[i][0]=scan.nextInt();
			ab[i][1]=scan.nextInt();
		}


		Arrays.sort(ab,new Comparator<int[]>(){
			@Override
			public int compare(int[] o1,int[] o2){
				return o1[0] -o2[0];
			}
		});

		int cnt=0;
		long ans=0;
		while(true){
			long k =ab[cnt][1];
			K-=k;
			if(K<=0){
				ans = ab[cnt][0];
				break;
			}
			cnt++;

		}
		System.out.println(ans);
	}

}