#include <cstdio>
bool NeChi(int Baof, double Hp, int Nwhp) {
	if (Nwhp / (Baof * 1.0) * Nwhp  > Hp) return true;
	else return false;
}
int main() {
	double happy = 0, sum = 0;
	int n, p;
	scanf ("%d", &n);
	for (int i = 1; i <= n; ++i) {
		scanf ("%d", &p);
		if (NeChi(i, happy, sum + p)) {sum += p; happy = sum / (i * 1.0) * sum;}//如果能吃掉，那么就吃掉
	}
	printf ("%.8lf", happy);
}