#include <iostream>
#include<fstream>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int P,N,ok=0,M,nr5=0;
int main()
{
   fin>>P;
   N=0;
   while(ok==0)
   { N=N+5;
   M=N;
    while(M%5==0)
    {
        M=M/5;
        nr5++;
    }
     if( nr5==P)
        ok=1;

   }
   while(N%5!=0)
    N--;
   fout<<N;
   return 0;
}