#include<fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
unsigned  int nr0;

unsigned  int fact(unsigned  int x)
{
unsigned int nr=0,cp=5;
while(x>=cp)
	{
		nr+=x/cp;
		cp*=5;
	}
return nr;
}
 int caut(unsigned int p,unsigned int u)
{
	unsigned int mij,f;
	if(p<=u)
		{
		mij=(p+u)/2;
		f=fact(mij);
		if(f==nr0)
			if(mij%10<5)
			return (mij/10*10);
			else return (mij/10*10+5);
		else
			if(nr0<f)
				return caut(p,mij-1);
			else    return caut(mij+1,u);
		}
	else return -1;
}

int main()
{
	f>>nr0;
	if(nr0>0)
		g<<caut(0,2000000000)<<'\n';
	else
		if(nr0==0)
			g<<1;
		else g<<-1;
	f.close();
	g.close();
	return 0;
}