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

#include <fstream>

using namespace std;

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