#include <bits/stdc++.h>
using namespace std;
#define int long long
#define rep(i,n) for(int (i)=0;(i)<(n);(i)++)
#define rrep(i,n) for(int (i)=((n)-1);(i)>=0;(i)--)
#define itn int
#define all(x) (x).begin(),(x).end()
#define F first
#define S second
const long long INF = 1LL << 60;
const int MOD = 1000000007;
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
int gcd(int a,int b)
{
    if (a%b==0) return(b);
    else return(gcd(b,a%b));
}
signed main(void){
    int m,n; cin>>m>>n;
    itn d = gcd(m,n);
    m /= d; n/=d;
    if(n == 1&& m==1) {cout<<0<<endl; return 0;}
    itn ans = 0;
    int x = (m-1)/n;
    ans += x;
    m -= n * x;
    if(m == 1 && n == 1) {cout<<ans<<endl; return 0;}
    ans++;
    int tmp = m;
    m = n;
    n = tmp;
    int y = (m-1)/n;
    ans += y;
    m -= n * y;
    if(m == 1 && n == 1) { cout<<ans<<endl; return 0;}
    ans++;
    tmp = m;
    m = n;
    n = tmp;
    x = (m-1)/n;
    ans += x;
    m -= n * x;
    if(m == 1 && n == 1) {cout<<ans<<endl; return 0;}
    else cout<<-1<<endl;
}