#include <fstream>
#include <cmath>
using namespace std;
int i,n,p,x;
ifstream in("fact.in");
ofstream out("fact.out");
    int pow(int base, int power) {
        if (power == 0) return 1;
        if (power == 1) return base;
        if (power % 2 == 0) return pow(base * base, power / 2);
        if (power % 2 == 1) return base * pow(base * base, power / 2);
    }


int main() 
{
	in >> p;
	x = pow(10,p);
	n=1;
	while(n%x!=0)
	{
		++i;
		n *= i;
	}
	if(n>pow(10,8))
	{
		out<<-1;
	} 
	else 
	{
		out<<i;
	}
	in.close();
	out.close();
	return 0;
}