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.*;

public class Main {
    static public void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int N = sc.nextInt();
        int K = sc.nextInt();

        Map<Integer, Long> map = new HashMap<>();

        for(int i = 0; i < N; i++) {
            int a = sc.nextInt();
            long b = sc.nextLong();
            map.put(a, map.getOrDefault(a, 0L) + b);
        }

        List<Integer> keys = new ArrayList(map.keySet());
        Collections.sort(keys);

        long count = 0;

        int ans = 0;
        for(int key: keys) {
            long newCount = count + map.get(key);
            if(count <= K && K <= newCount) {
                ans = key;
                break;
            }
            count = newCount;
        }

        System.out.println(ans);
    }
}