include <bits/stdc++.h>

using namespace std;

int main() {

bool f = true;
long long  n, i, d, s;
cin >> n >> d;

for ( i = 2; i < sqrt(n); i++) {

	if (n % i == 0 &&  n / i - i <= d) {
		s = n / i;
		f = false;
		break;
	}
}

if (f == true) {
	cout << "-1";
} else
	cout << s;
return 0;

}