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: Time Limit Exceeded)

#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <map>
#include <climits>
#include <math.h>
#include <utility>
using namespace std;

typedef long long ll;
typedef vector<bool> vb;
typedef vector<char> vc;
typedef vector<long long> vll;
typedef vector<int> vi;
typedef vector<string> vs;
typedef vector<vector<bool>> vvb;
typedef vector<vector<int>> vvi;

#define rep(i,n) for(int (i)=0;(i)<(n);(i)++)
#define all(a) a.begin(),a.end()

int main() {
	int n, k;
	cin >> n >> k;
	vi a(n), b(n);
	rep(i, n) {
		cin >> a.at(i) >> b.at(i);
	}
	rep(i, n) {
		for (int j = i; j < n; j++) {
			if (a.at(i) > a.at(j)) {
				swap(a.at(i), a.at(j));
				swap(b.at(i), b.at(j));
			}
		}
	}
	int cnt = 0;
	rep(i, n) {
		cnt += b.at(i);
		if (cnt >= k) {
			cout << a.at(i) << endl;
			return 0;
		}
	}
	return 0;
}