#include<iostream>

using namespace std;

int main()
{
	long n, nn, d, dd, a, b;
	cin >> n >> d;

	nn = n;
	dd = d;
	while (1){
		a = n % d;
		if (a == 0) break;
		n = d;
		d = a;
	}
	b = nn * dd / d / dd - 1;

	cout << b << endl;

	return 0;

}