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) throws Exception {
        Scanner sc = new Scanner(System.in);
      
        int N = Integer.parseInt(sc.next());
      
        long K = Long.parseLong(sc.next());
      
        int[] a = new int[N];
      //aer augeworaw
        long[] b = new long[N];
      
        Map<Integer, Long> map = new TreeMap<>();
        for(int i=0; i<N; i++) {
            a[i] = Integer.parseInt(sc.next());
            b[i] = Long.parseLong(sc.next());
            if(map.containsKey(a[i])) map.put(a[i], map.get(a[i])+b[i]);
            else map.put(a[i], b[i]);
        }
        long sum = 0;
        int ans = 0;
        for(int i : map.keySet()) {
            
            sum += map.get(i);
            if(sum >= K) {
                ans = i;
                break;
            }
        }
        System.out.println(ans);
        
    }   
}