#include <iostream>

using namespace std;
int total;
int res;
int demand;
const int N = (int)1e5 + 100;
struct node {
	long long len;
	long long b;
}nodes[N];
inline bool check(int x) {
	int count = 0;
	long long whole = 0;
	for (int i = 0; i < total; i++) {
		if (x > nodes[i].len || x > nodes[i].b) {
			continue;
		}
		else {
			whole = nodes[i].len * nodes[i].b;
			long long need = (long)x * (long)x;
			int see = 0;
			see= whole / need;
			count += see;
		}
	}

	bool shit=count >= demand;
	return shit;
}
int main() {
	cin >> total >> demand;
	int right = 0;
	for (int i = 0; i < total; i++){
		int bind_1, bind_2;
		cin >> bind_1 >> bind_2;
		right = max(right, bind_1);
		right = max(right, bind_2);
		nodes[i].len = bind_1;
		nodes[i].b = bind_2;
	}
	int left = 1;
	while (left <= right) {
		int mid = right + left >> 1;
		if (check(mid)) {
			res = mid;
			left = mid + 1;


		}
		else {
			right = mid - 1;

		}
	}
	cout << res << endl;
	return 0;
}