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: Accepted)

#include <bits/stdc++.h>
using namespace std;

int main(){

  long long N, K;
  cin >> N >>K;
  vector<pair <long long,long long> > array(N);

  for(int i = 0; i < N; i++){
    int a,b;
    cin >> a >> b;
    array.at(i).first = a;
    array.at(i).second = b;
  }
  
  sort(array.begin(),array.end());


  long long counter = 0;
  long long answer = 0;
  for(auto num : array){
    counter += num.second;
    if (counter >= K) {
      answer = num.first;
      break;
    }
  }
  cout << answer << endl;
}