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