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{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int k = sc.nextInt();
    List<Integer> list = new ArrayList<>();
    Map<Integer, Integer> map = new HashMap<>();
    for(int i = 0; i < n; i++){
      int a = sc.nextInt();
      int b = sc.nextInt();
      if(!map.containsKey(a)){
        map.put(a, 0);
        list.add(a);
      }
      map.put(a, map.get(a) + b);
    }
    long sum = 0;
    Collections.sort(list);
    for(int i : list){
      sum += map.get(i);
      if(sum >= k){
        System.out.println(i);
        System.exit(0);
      }
    }
  }
}