#include <bits/stdc++.h>
using namespace std;

#define REP(i,n) for(int i=0;i<n;i++)
#define rep(i,n) for(int i=0;i<n;i++)
#define INF 1<<29
#define LINF LLONG_MAX/3
#define MP make_pair
#define PB push_back
#define EB emplace_back
#define ALL(v) (v).begin(),(v).end()
#define debug(x) cerr<<#x<<":"<<x<<endl
#define debug2(x,y) cerr<<#x<<","<<#y":"<<x<<","<<y<<endl
template<typename T> ostream& operator<<(ostream& os,const vector<T>& vec){ os << "["; for(const auto& v : vec){ os << v << ","; } os << "]"; return os; }

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;

ll N,D;

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

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


    if(N==D){
        cout << 0 << endl;
        return 0;
    }

    ll m=gcd(N,D);

    cout << N / m - 1 << endl;
}