#include <fstream>
 using namespace std;
 long long nrz(long long c)
   {
    long p=0;
    while(c)
      {
       p+=c/5;
       c/=5;
      }
     return p;
   }
 int main()
   {
    ifstream f("fact.in");
    ofstream g("fact.out");
    long long int p,st,dr,m;
	f>>p;
	st=1;
	dr=100000000000;
	while (st<dr)
	{
		m=(st+dr)/2;
		if (nrz(m)<p)
			st=m+1;
		else
			dr=m;
	}
	if (nrz(st)==p)
		g<<st;
	else
		g<<-1;
	f.close();
	g.close();
	return 0;
}