#include <fstream>
#include <math.h>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
long int facto (long int r)
{
long int i,m;
m=1;
for(i=1;i<=r;i++)
{
	m=m*i;
}
return m;
}

long int putere(long int h)
{
long int i,o;
o=1;
for(i=1;i<=h;i++)
{
o=o*10;
}
return o;
}

int main()
{
	long int t,n,s,l;
	int k;
	while(f>>t)
	{
	t=putere(t);
	n=1;
	l=-1;
	k=0;
	while(k==0 && n<=100000000)
	{
	s=facto(n);
	if(s%t==0){
		k=1;
		l=n;
	}else{
	n++;
	}
	}
	g<<l<<endl;
	}
	f.close();
	g.close();
}