#include <bits/stdc++.h>

using namespace std;

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()

template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
template<typename A, typename B> inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; }

typedef unsigned long long ull;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<int, pii> P;

const ll INF = 1ll<<60;
const ll MOD = 1000000007;
const double EPS  = 1e-10;

ll gcd(ll a, ll b) {
	if (b == 0) return a;
	return gcd(b, a % b);
}

int main() {
	ll n, d;
	cin >> n >> d;
	
	ll ans = -1, pos = 0;
	
	if (gcd(n, d) == 1) ans = n - 1;
	else {
		set<int> ss;
		ss.insert(0);
		
		while (true) {
			ll last = (n - pos - 1) / d * d;
			if (pos + d >= n) last = pos;
			
			ans += (last - pos) / d + 1;
			
			pos = (last + d) % n;
			
			if (ss.find(pos) != ss.end()) break;
			ss.insert(pos);
		}
	}
	cout << ans << endl;
	
	return 0;
}