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 C++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <stdio.h>
#include <iostream>
 
int main(void)
{
  long long n, k;
  long long a, b;
  const int AMAX = 100000;
  long long cnt1[AMAX + 1];
  long long cnt2[AMAX + 1];
  long long c = 0;
  long long t = 0;
  
  std::cin >> n >> k;
  
  for(long long i = 0; i < n; i++)
  {
    std::cin >> a >> b;
    cnt1[c] = a;
    cnt2[c++] = b; 
  }
  
  for(long long j = 0; j < c; j++)
  {
    
    if(	t <= k && (t + cnt2[j+1]) > k)
    {
      std::cout << cnt1[j] << std::endl;
      break;
    }
    
    t += cnt2[j];
  }
  
  return 0;
}