#include <cstdio>
using namespace std;
FILE *f=fopen("fact.in","r");
FILE *g=fopen("fact.out","w");
int main()
{int p,n,x;
fscanf(f,"%d",&p);
if (p==0) fprintf(g,"1\n");
     else {n=0;
           while (p!=0) {n+=5;
                         p--;
                         x=n/5;
                         while (x%5==0) {p--;x/=5;}
                        }
           fprintf(g,"%d\n",n);
           }


return 0;
}