#include using namespace std; typedef long long ll; ll gcd(ll a, ll b){ if(b == 0)return a; return gcd(b, a % b); } int main(){ ll N, M; cin >> N >> M; ll g = gcd(N, M); N /= g; M /= g; int e2 = 0, e5 = 0; while(M % 2 == 0){ M /= 2; ++e2; } while(M % 5 == 0){ M /= 5; ++e5; } if(M != 1){ cout << -1 << endl; return 0; } int maxi = max(e2, e5); e2 = maxi - e2; e5 = maxi - e5; N %= 10; while(e2--){ N = (N * 2) % 10; } while(e5--){ N = (N * 5) % 10; } cout << N << endl; return 0; }