#include<fstream.h>


int cinci(int x)
{
  long p=0;
  while(x>=5)
    p+=x/5,x/=5;
  return p;
}
int main()
{
  long p,x,ante;
  ifstream in("fact.in");
  ofstream out("fact.out");
  in>>p;
  long z=p;
  x=p;
  while(z)
    x-=z/5,z/=5;
  z=p/5;
  while(z>=5)
    x+=(z/5),z/=5;
  x*=5;
  if(x==0) x=1;
  if(p==cinci(x)) out<<x;
    else out<<-1;
  return 0;
}