#include #define rep(i,n) for(int i = 0; i < (n); ++i) #define srep(i,s,t) for (int i = s; i < t; ++i) #define drep(i,n) for(int i = (n)-1; i >= 0; --i) using namespace std; typedef long long int ll; typedef pair P; #define yn {puts("Yes");}else{puts("No");} #define MAX_N 200005 long long int GCD(long long int x, long long int y){ if(x>y){ long long int swap = x; x = y; y = swap; } while(true){ if(y%x==0){ return x; }else{ long long int amari = y%x; y = x; x = amari; } } } int main() { int f[4] = {}; int a, b; cin >> a >> b; ll g = GCD(a,b); a /= g; b /= g; if(a <= 3)f[a] = 1; if(b <= 3)f[b] = 1; int cnt = 0; rep(i,4)cnt += f[i]; ll ans = -1; if(cnt == 2){ srep(i,1,4){ if(f[i] == 0)ans = i; } } cout << ans * g << endl; return 0; }