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 {
	
	private void doit(){
		Scanner sc = new Scanner(System.in);
		while(sc.hasNext()){
			int n = sc.nextInt();
			long k = sc.nextLong();
			
			ArrayList<Long> data = new ArrayList<>();
			HashMap<Long, Long> map = new HashMap<>();
			for(int i = 0; i < n;i++){
				long a = sc.nextInt();
				long b = sc.nextInt();
				if(map.containsKey(a)){
					map.put(a, map.get(a) + b);
				}
				else{
					map.put(a,b);
					data.add(a);
				}
			}
			Collections.sort(data);
			
			long sum = 0;
			for(long ind: data){
				long val = map.get(ind);
				sum += val;
				if(sum >= k){
					System.out.println(ind);
					break;
				}
			}

		}
	}

	private void debug(Object... o) {
		System.out.println("debug = " + Arrays.deepToString(o));
	}

	public static void main(String[] args) {
		new Main().doit();
	}

}