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();
        Map<Long, Long> map = new TreeMap<>();
        long[][] a = new long[2][N];
        for(int i = 0; i < N; i++){
            a[0][i] = sc.nextInt();
            a[1][i] = sc.nextInt();
            if(map.containsKey(a[0][i]))
                map.put(a[0][i], map.get(a[0][i]) + a[1][i]);
            else
                map.put(a[0][i], a[1][i]);
        }
        sc.close();
        
        long sum = 0;
        for(Long key: map.keySet()){
            sum += map.get(key);
            if(sum >= K){
                System.out.println(key);
                return;
            }
        }
    }
}