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 <algorithm>
#include <cctype>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <functional>
#include <iostream>
#include <list>
#include <map>
#include <memory>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>
using namespace std;

#define EPS 1e-10
#define INF 1000000000
#define mp make_pair
#define pb push_back

typedef vector<int> vi;
typedef vector<vi> vii;
typedef pair<int,int> pii;
typedef long long ll;

int main() {
  int N, K;
  cin >> N >> K;
  map<int, int> counts;
  set<int> nums;
  for (int i = 0; i < N; i++) {
    int a, b;
    cin >> a >> b;
    nums.insert(a);
    counts[a] += b;
  }
  int ans = 0;
  set<int>::iterator it;
  for (it = nums.begin(); it != nums.end(); it++) {
    K -= counts[*it];
    ans = *it;
    if (K <= 0) {
      break;
    }
  }
  cout << ans << endl;
}