#include <bits/stdc++.h>

#define i64 long long int

#define pii pair<int, int>
#define mp make_pair
#define fi first
#define se second

#define eb emplace_back

using namespace std;

inline int Read() {int res; return scanf("%d", &res), res; }
inline i64 Read64() {i64 res; return scanf("%lld", &res), res; }

const int INF_32 = 1e9;
const i64 INF_64 = 1e18;

const int N = 500000 + 5;

int n, q[N], hea, tai;
double p[N], f[N];

int main() {
	n = Read();
	for(int i = 1; i <= n; ++ i) scanf("%lf", &p[i]);
	
	f[n] = p[n] * n;
	double ans = f[n];
	hea = 1, q[++ tai] = n;
	for(int i = n - 1; i >= 1; -- i) {
		while(hea < tai && f[q[hea]] - p[q[hea]] * i < f[q[hea + 1]] - p[q[hea + 1]] * i) hea ++;
		f[i] = (f[q[hea]] - p[q[hea]] * i) * p[i] + i * p[i];
		ans = max(ans, f[i]);
		while(hea < tai && (f[i] - f[q[tai]]) / (p[i] - p[q[tai]]) > (f[q[tai]] - f[q[tai - 1]]) / (p[q[tai]] - p[q[tai - 1]])) tai --;
		q[++ tai] = i;
	}
	
	printf("%.12lf\n", ans);
	
	return 0;
}