long a,b,s;main(i){for(scanf("%ld",&b);~b&1;s+=i)b/=2;for(;b%5<1;s-=i)b/=5;a?a=!printf("%d",a%b?-1:s<0?5:a/b%10*(s?1<<s%4:1)%10):main(-1,a=b);}