#include<fstream>
#include<math.h>
using namespace std;
int main()
{
	ifstream f("fact.in");
	ofstream g("fact.out");
	int p;
	f>>p;
	int i=5;

	if(p==0)
	{
		g<<1<<endl;
	}
	else
	{
		int zerouri = 1;
		while(p > (zerouri * 5 + 1)) {
			zerouri = zerouri * 5 + 1;
			i *= 5;
		}
		i += 5;
		while(p > zerouri)
		{
			int ci=i;
			while(ci%5==0)
			{
				zerouri++;
				ci/=5;
			}
			i+=5;
		}
		if(p != zerouri)
		{
			g<<-1<<endl;
		}
		else
			g<<(i-5)<<endl;
	}
	f.close();
	g.close();
	return 0;
}