#include <bits/stdc++.h>
using namespace std;

void solve_() {
    int n;
    cin >> n;
    vector<double> p(n);
    for (int i = 0; i < n; ++i) {
        cin >> p[i];
    }
    vector<double> dp(n);
    dp[n - 1] = p[n - 1] * n;
    vector<array<double, 3>> st;
    st.push_back({1 - p[n - 1], dp[n - 1], (double)n});
    int ptr = 0;
    for (int i = n - 2; i >= 0; --i) {
        ptr = min(ptr, (int)st.size() - 1);
        while (ptr + 1 < (int)st.size() && (i + 1) * st[ptr + 1][0] + st[ptr + 1][1] > (i + 1) * st[ptr][0] + st[ptr][1]) {
            ++ptr;
        }
        dp[i] = p[i] * ((i + 1) * st[ptr][0] + st[ptr][1]);
        while (!st.empty() && dp[i] + (1 - p[i]) * st.back()[2] > st.back()[1] + st.back()[0] * st.back()[2]) {
            st.pop_back();
        }
        double x = n;
        if (!st.empty()) {
            double k = st.back()[0];
            double b = st.back()[1];
            double k1 = (1 - p[i]);
            double b1 = dp[i];
            x = (b1 - b) / (k - k1);
        }
        st.push_back({1 - p[i], dp[i], x});
    }
    double ans = 0;
    for (int i = 0; i < n; ++i) {
        ans = max(ans, dp[i]);
    }
    cout << ans << '\n';
}

/// #define MULTITEST

signed main() {
#ifdef LOCAL
    freopen("../input.txt", "r", stdin);
    freopen("../output.txt", "w", stdout);
#else
    ios_base::sync_with_stdio(false);
    cin.tie(0);
#endif

    cout << fixed << setprecision(20);

    int tst = 1;
#ifdef MULTITEST
    cin >> tst;
#endif // MULTITEST
    while (tst--) {
        solve_();
    }
    return 0;
}