#include <bits/stdc++.h>
using namespace std;
using ll=long long;
using ld=long double;
const ll ILL=2167167167167167167;
const int INF=2100000000;
#define rep(i,a,b) for (int i=(int)(a);i<(int)(b);i++)
#define all(p) p.begin(),p.end()
template<class T> using _pq = priority_queue<T, vector<T>, greater<T>>;
template<class T> ll LB(vector<T> &v,T a){return lower_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> ll UB(vector<T> &v,T a){return upper_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> bool chmin(T &a,T b){if(b<a){a=b;return 1;}else return 0;}
template<class T> bool chmax(T &a,T b){if(a<b){a=b;return 1;}else return 0;}
template<class T> void So(vector<T> &v) {sort(v.begin(),v.end());}
template<class T> void Sore(vector<T> &v) {sort(v.begin(),v.end(),[](T x,T y){return x>y;});}
bool yneos(bool a,bool upp=0){if(a){cout<<(upp?"YES\n":"Yes\n");}else{cout<<(upp?"NO\n":"No\n");}return a;}
template<class T> void vec_out(vector<T> &p,int ty=0){
    if(ty==2){cout<<'{';for(int i=0;i<(int)p.size();i++){if(i){cout<<",";}cout<<'"'<<p[i]<<'"';}cout<<"}\n";}
    else{if(ty==1){cout<<p.size()<<"\n";}for(int i=0;i<(int)(p.size());i++){if(i) cout<<" ";cout<<p[i];}cout<<"\n";}}
template<class T> T vec_min(vector<T> &a){assert(!a.empty());T ans=a[0];for(auto &x:a) chmin(ans,x);return ans;}
template<class T> T vec_max(vector<T> &a){assert(!a.empty());T ans=a[0];for(auto &x:a) chmax(ans,x);return ans;}
template<class T> T vec_sum(vector<T> &a){T ans=T(0);for(auto &x:a) ans+=x;return ans;}
int pop_count(long long a){int res=0;while(a){res+=(a&1),a>>=1;}return res;}

template< typename T >
struct LiChaoTree {
    struct Line {
        T a, b;

        Line(T a, T b) : a(a), b(b) {}

        inline T get(T x) const { return a * x + b; }

        inline bool over(const Line &b, const T &x) const {
            return get(x) < b.get(x);
        }
    };

    vector< T > xs;
    vector< Line > seg;
    int sz;

    LiChaoTree(const vector< T > &x, T INF) : xs(x) {
        sz = 1;
        while(sz < xs.size()) sz <<= 1;
        while(xs.size() < sz) xs.push_back(xs.back() + 1);
        seg.assign(2 * sz - 1, Line(0, INF));
    }

    void update(Line &x, int k, int l, int r) {
        int mid = (l + r) >> 1;
        auto latte = x.over(seg[k], xs[l]), malta = x.over(seg[k], xs[mid]);
        if(malta) swap(seg[k], x);
        if(l + 1 >= r) return;
        else if(latte != malta) update(x, 2 * k + 1, l, mid);
        else update(x, 2 * k + 2, mid, r);
    }

    void update(T a, T b) { // ax+b
        Line l(a, b);
        update(l, 0, 0, sz);
    }

    T query(int k) { // xs[k]
        const T x = xs[k];
        k += sz - 1;
        T ret = seg[k].get(x);
        while(k > 0) {
            k = (k - 1) >> 1;
            ret = min(ret, seg[k].get(x));
        }
        return ret;
    }
};

void solve();
// CITRUS CURIO CITY / FREDERIC
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int t = 1;
    // cin >> t;
    rep(i, 0, t) solve();
}

void solve(){
    int N;
    cin >> N;
    vector<ld> p(N), C(N);
    rep(i, 0, N) cin >> p[i], C[i] = p[i];
    vector<ld> dp(N);
    vector<ld> X(N);
    rep(i, 0, N) X[i] = (ll)(i + 1);
    LiChaoTree<ld> L(X, INF);
    for (int i = N - 1; i >= 0; i--){
        if (i + 1 == N){
            dp[i] = X.back() * C.back();
        }
        else{
            // cout << L.query(i) << endl;
            dp[i] = -C[i] * L.query(i);
        }
        L.update(-(1 - C[i]), -dp[i]);
    }
    // vec_out(C);
    // vec_out(dp);
    cout << setprecision(18) << fixed << vec_max(dp) << "\n";
}