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.Scanner;
import java.util.TreeMap;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner scan = new Scanner(System.in);
        int N = scan.nextInt();
        int K = scan.nextInt();
        int a, b;
        int kValue, aValue, bValue;
        TreeMap<Integer, Integer> numberMap = new TreeMap<Integer, Integer>();
        int answer = 0;
        
        for(int i = 0; i < N; i++) {
            a = scan.nextInt();
            b = scan.nextInt();
            
            if(numberMap.containsKey(a)) {
                bValue = numberMap.get(a);
                numberMap.put(a, b + bValue);
            } else {
                numberMap.put(a, b);
            }
        }
        
        kValue = K;
        while(kValue > 0 && !numberMap.isEmpty()) {
            aValue = numberMap.firstKey();
            answer = aValue;
            bValue = numberMap.get(aValue);
            
            numberMap.remove(aValue);
            
            kValue -= bValue;
        }
        
        System.out.println(answer);
    }
}