#include<stdio.h>
#include<math.h>
long long n,p,q,x,nr5,i;
int main()
{
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    scanf("%lld",&n);
    if(n==0) printf("1"); 
    else
    {
        p=5*(n-n/5);
        if(p<0) p=4;
        while(nr5<n)
        {
               p++;
               x=1;
               nr5=0;
               for(;;)
               {
                                x=x*5;
                                nr5=nr5+p/x;
                                if(x*5>p) break;
               }
        }
        if(nr5==n) printf("%lld",p);
               else printf("-1");
    }
    return 0;
}