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



int main()
{
    int n,p,i=0,m;

    ifstream f("fact.in");
	ofstream g("fact.out");

	f>>p;
  
   
    
    n=1;
	
    
    while(p!=i)
    {
               n++;
               if(n%5==0)
                {
                         m=n; 
                         while(m%5==0) 
                           {
                              i++;
                               m=m/5;
                            }
    }           }
      
      g<<n;
     
      }