#include <bits/stdc++.h>
#define x first
#define X first
#define y second
#define Y second
#define pb push_back
#define PB push_back

using namespace std;

typedef long long ll;
typedef pair<int,int> pii;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef long double ld;
typedef pair<ld, ld > pt;

const int N = 5e5 + 500;
const int INF = 0x3f3f3f3f;
const int MOD = 998244353;
const char en='\n';
const ll LLINF=1ll<<60;

inline ld ccw(pt A, pt B, pt C) {
	return A.X * (B.Y - C.Y) + B.X * (C.Y - A.Y) + C.X * (A.Y - B.Y); 
}

struct hull {
	vector < pt > cur;
	void add(pt nw) {
		while((int)cur.size() >= 2 && ccw(cur[(int)cur.size() - 2], cur.back(), nw) <= 0) {
			cur.pop_back();
		}
		cur.PB(nw);
	}
	ld get(int i, ld x) {
		if(i >= (int)cur.size() || i < 0) return 0;
		return cur[i].X * x + cur[i].Y;
	}
	ld query(ld x) {
		int lo = 0, hi = (int)cur.size() - 1;
		while(lo < hi) {
			int mid = (lo + hi) / 2;
			if(get(mid, x) >= get(mid + 1, x)) {
				hi = mid;
			} else {
				lo = mid + 1;
			}	
		}
		return get(lo, x);
	}
};

int n;
ld p[N], dp[N];

int main() {
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	hull H;
	cin >> n;
	for(int i = 1;i <= n;i++) {
		cin >> p[i];
	}
	cout << fixed << setprecision(12);
	dp[n] = p[n] * n;
	H.add({1 - p[n], dp[n]});
	ld ans = dp[n];
	for(int i = n - 1;i >= 1;i--) {
		dp[i] = p[i] * H.query(i);
		H.add({1 - p[i], dp[i]});
		ans = max(ans, dp[i]);
	}
	cout << ans << endl;
	return 0;
}