#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<n;i++)
#define int long long
using namespace std;

int N, D;

int gcd(int a, int b) {
  return b != 0 ? gcd(b, a % b) : a;
}

signed main()
{
	cin >> N >> D;

	if (gcd(N, D) == 1) {
		cout << N - 1 << endl;
		return 0;
	}

	int gcdx = gcd(N, D);
	cout << N / gcdx - 1 << endl;
}