#include<cstdio>
#include<fstream.h>
using namespace std;
int main()
{int n,p,i,r,a,b,k,j;
ifstream f("fact.in");
ofstream g("fact.out");
f>>p;
n=0;
do
{b=p;
k=0;
	n++;
r=1;
	for(i=1;i<=n;i++)
	r=r*i;
	for(j=b;j>=1;j--)
	{ 
		a=r%10;
		if (a==0)
			{
			k++;
		    r=r/10;}
	
	}
}
while((k!=p)||(n==10000));
if (k==p)
	g<<n;
else
	g<<-1;
f.close();
g.close();}