#include <stdio.h>

long P, N, N1, P1;

int main() {
	freopen("fact.in", "r", stdin);
	freopen("fact.out", "w", stdout);
	scanf("%ld", &P);
	if(P == 0){ printf("1"); P1 = -1;}
	else {
		for(N = 5; N <= P * 5; N += 5) {
			N1 = N;
			P1 = 0;
			while(N1 != 0) {
				P1 += N1 / 5;
				N1 /= 5;
			}
			if(P1 == P) {
				printf("%ld", N);
				P1 = -1;
				break;
			}
		}
	}
	if(P1 != -1) {
		printf("-1");
	}
	return 0;
}