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: Wrong Answer)

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();
      int[] a = new int[n];
      int[] b = new int[n];
      long sum = 0;
      TreeMap<Integer,Integer> map = new TreeMap<Integer,Integer>();
      for(int i = 0;i < n;i++){
        a[i]=sc.nextInt();
        b[i]=sc.nextInt();
        if(map.containsKey(a[i])) map.put(a[i],map.get(a[i])+b[i]);
        else map.put(a[i],b[i]);
      }
      Arrays.sort(a);
      int s = 0;
      while(sum < k){
      	sum += (long)map.get(a[s]);
        s++;
      }
      System.out.println(a[s-1]);
    }
}