#include<stdio.h>
#include<fstream.h>

int main()  
{
long p,n,tt,t,k5=0;  
//ifstream in("fact.in");  
//ofstream out("fact.out");  
freopen("fact.in","r",stdin);  
freopen("fact.out","w",stdout);  
scanf("%ld ",&p);  
//in>>p;  
//in.close();  

t=0;  
do {  
t+=5;  
tt=t;  
while(!(tt%50))  
{tt=tt/5;  
                k5++;}  
      }while(k5!=p);  
   
 //out<<t;}  
 //out.close();  
if(p==0)
  printf("1");
else   
 printf("%ld",t/10);

 return 0;  
 }