// Afla ce numar factorial are p cifre de zero la final

#include <fstream>

using namespace std;

bool multipleFive(int n) {
	int m = 1;
	while ((n!=m) && (n<m)) {
		m *= 5;
	}
	if (n==m) return true;
	else return false;
}

int main() {
	FILE* fin = fopen("fact.in","r");
	FILE* fout = fopen("fact.out","w");
	int p=0, n=0;
	fscanf(fin, "%d", &p);
	fclose(fin);
	for (int i=1; i<=p; i++) {
		n += 5;
		if (multipleFive(i)) { 
			i++;
			if (p<i)
				fprintf(fout, "%d", -1);
		}
	}
	fprintf(fout, "%d", n);
	return 0;
}