#include<fstream>
#include<math.h>
using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");
long long p,x=5,n,s;
int main()
{
	in>>p;
	n=5*p-1;
	while (x<n)
	{
		x*=5;
		s+=n/x;
	}
	n-=5*s-1;
	s=0;
	for (int i=1;i<=n;i++)
	{
		x=i;
		while (x%5==0)
		{
			x/=5;
			s++;
		}
	}
	if (p==0)
		out<<"1";
	else
		if(s!=p)
			out<<"-1";
		else
			out<<n;
	in.close();
	out.close();
	return 0;
}