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

int main() {
  int N, K;
  std::cin >> N >> K;
  //N = 100;
  std::vector<int> a(N), b(N);
  for(int i=0; i<N; i++) {
    std::cin >> a.at(i) >> b.at(i);
  }
  /*for(int i=0; i<N; i++) {
    a.at(i) = i;
    b.at(i) = i * i;
  }*/
  
  map<int,int> m;
  for(int i=0; i<N; i++) {
    m[a[i]] = b[i];
  }
  
  /*vector<int> a2(N,999999), b2(N,999999);
  a2.at(0) = a.at(0);
  b2.at(0) = b.at(0);
  for(int i=1; i<N; i++) {
    for(int j=0; j<i+1; j++) {
      if(a.at(i) < a2.at(j)) {
        for(int k=N-2; k>j-1; k--) {
          a2.at(k+1) = a2.at(k);
          b2.at(k+1) = b2.at(k);
        }
        a2.at(j) = a.at(i);
        b2.at(j) = b.at(i);
        break;
      }
    }
  }*/
  int count = 0;
  /*for(int i=0; i<N; i++) {
    count += b.at(i);
    if(count>=K) {
      cout << a.at(i) << endl;
      break;
    }
  }*/
  for(auto it=m.begin(); it!=m.end(); it++) {
    count += it->second;
    cerr << it->first << endl;
    if(count>=K) {
      cout << it->first << endl;
      break;
    }
  }
}