#include <iostream>
#include<fstream>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int P,N,ok=0,M,nr2=0,nr5=0;
int main()
{
   fin>>P;
   N=0;
   while(ok==0)
   {
       N++; M=N;

        while(M%5==0)
       {
           M=M/5;
           nr5++;
       }
     if( nr5>=P)
        ok=1;

   }
   fout<<N;
   return 0;

}