#include <fstream>

using namespace std;

ifstream f("fact.in");
ofstream g("fact.out");

int main() {
	int k,p,n,pow;

	f>>p;
	n = 4*p, k = 0; pow = 5;
	while(n/pow) k += n/pow, pow *= 5;
	n = 5*(n/5+1);
	do {
		pow = 5, k = 0;
		while(n/pow) k += n/pow, pow *= 5;
		n += 5;
	} while(k < p);
	n -= 5;
	if(p == 0) g<<1;
	else {
		if(k == p) g<<n;
		else g<<-1;
	}
	return 0;
}