#include<stdio.h>
#include<math.h>
int s=0,pp=5,n=0,p,x;
FILE *f,*g;
int main ()
{

f=fopen("fact.in","r");
fscanf(f,"%d",&p);fclose(f);
g=fopen("fact.out","w");
if(p==0)fprintf(g,"%d",1);
	else if(p==1)fprintf(g,"%d",5);
	else{	while(s<p){s=s+pp-1;pp*=5;n++;}
			x=int((p+n-1)*4*pow(5,n)/(pow(5,n)-1));
				fprintf(g,"%d",x);}

fclose(g);
return 0;

}