#include <fstream>

using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
long long n,p,t,ok=1;
long long i=0;
int main()
{
    f>>p;
    if(p==0)g<<1<<'\n';
      else while(ok==1){ i=i+5;

                         for(int j=5;j<=i;j=j*5)if(i/j>0)t=t+i/j;
                                                else j=i;
                          if(t==p){g<<i<<'\n';
                                   ok=0;
                                  }
                           else  if(t>p){g<<-1<<'\n';
                                         ok=0;
                                         }

                         t=0;
                      }
    return 0;
}