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)

// C.

#include <iostream>
#include <sstream>
#include <algorithm>
#include <vector>

using namespace std;

typedef long long LL;

int main(int argc, char* argv[]) {
	while (true) {
		LL n = -1, k = -1;
		cin >> n >> k;
		if (n <= 0) break;
		vector<pair<LL, LL>> v(n);
		for (LL i = 0; i < n; ++i) {
			cin >> v[i].first >> v[i].second;
		}
		sort(v.begin(), v.end());
		for (LL i = 0; i < n; ++i) {
			if (k <= v[i].second) {
				cout << v[i].first << endl;
				break;
			}
			k -= v[i].second;
		}
	}
	return 0;
}