#include <stdio.h>
FILE *f,*g;
int main()
{long int p,n,d,j;
int k,i;
f=fopen("fact.in","r");
fscanf(f,"%ld",&p);
fclose(f);
g=fopen("fact.out","w");
n=0;
if(p==0) fprintf(g,"1");

if(p<0)  fprintf(g,"-1");

if(p>0) {while(p>=6){k=0;d=1;
		  while(p>=d*5+1){k++;d=d*5+1;}
		  p=p-d;
		  d=5;
		  for(i=1;i<=k;i++) d=5*d;
		  n=n+d;
		  }
	 for(i=0;i<p;i++) n=n+5;
	 fprintf(g,"%ld",n);

	 }
fclose(g);
return 0;
}