#include <fstream>
#include <climits>
using namespace std;

ifstream fin("fact.in");

ofstream fout("fact.out");

 

int n,p,st,dr,mij,gasit;

 

int zerouri(int x)

{

    int s=0,putere=5;

    while(x>=putere)

    {

      s+=x/putere;

      putere*=5;

    }

    return s;

}

 

int main()

{

   fin>>p;

   if(p==0) fout<<1;

   else

   {

      st=1;dr=500000000;

      while(st<=dr)

      {

          mij=st+(dr-st)/2;

          int p1=zerouri(mij);

          if(p==p1)

          {

              gasit=1;n=mij;break;

          }

          else if(p<p1)

                    dr=mij-1;

               else

                    st=mij+1;

      }

      if(!gasit)fout<<-1;

      else fout<<n-n%5;

   }

}