#include <iostream>
#include <fstream>
#include <cstdio>
#include <cmath>
#include <vector>
#include <cstring>
#include <string>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <algorithm>
using namespace std;

#define REP(i,n) for(int i=0; i<n; ++i)
#define FOR(i,a,b) for(int i=a; i<=b; ++i)
#define FORR(i,a,b) for (int i=a; i>=b; --i)
#define pi M_PI

typedef long long ll;
typedef vector<int> VI;
typedef vector<ll> VL;
typedef vector<VI> VVI;
typedef pair<int,int> P;
typedef pair<ll,ll> PL;

int gcd(int x, int y){
    if (y == 0) return x;
    return gcd(y, x%y);
}


int main(){
    int n, d;
    cin >> n >> d;

    int ans;
    if (n == d) ans = 0;
    else ans = n/gcd(n,d)-1;

    cout << ans << endl;

    return 0;
}