#include <iostream>
using namespace std;

int gcd(int m,int n){
	while(n != 0){
		int tmp = n;
		n = m % n;
		m = tmp;
	}
	return m;
}

int main(){
	int n,d;
	cin >> n >> d;
	cout << (gcd(n,d) == 1 ? --n : n / d - 1) << endl;;
}