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.Arrays;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class Main {
	public static void main(String args[]){

		Scanner cin = new Scanner(System.in);
		int N = cin.nextInt();
		long K = cin.nextLong();
		long sum = 0L;
		int result=0;
		Map<Integer,Long> mapv = new HashMap<>();
		for(int i=0;i<N;i++){
			int tmp1 = cin.nextInt();
			long tmp2 = cin.nextLong();
			if(mapv.containsKey(tmp1)){
				mapv.put(tmp1, mapv.get(tmp1)+tmp2);
			}else{
				mapv.put(tmp1, tmp2);
			}
		}
		cin.close();
		int value[] = new int [mapv.size()];
		int count =0;
		for(Integer n : mapv.keySet()){
			value[count] = n;
			count++;
		}
		Arrays.sort(value);

		for(int j=0;j<value.length;j++){
			sum += mapv.get(value[j]);
			if(K<=sum){
				result = value[j];
				break;
			}
		}
		System.out.println(result);
	}
}