#include <bits/extc++.h>

int main(){
    using namespace std;
    unsigned long N;
    cin >> N;
    vector<pair<unsigned long, unsigned long>> problems(N);
    for(auto&& [a, _] : problems)cin >> a;
    for(auto&& [_, b] : problems)cin >> b;
    reverse(begin(problems), end(problems));
    vector<pair<unsigned long, unsigned long>> stack;
    while(!empty(problems)){
        auto [a, b]{problems.back()};
        problems.pop_back();
        while(!empty(stack) && (stack.back().first / stack.back().second > a / b || (stack.back().first / stack.back().second == a / b && (stack.back().first % stack.back().second) * b / stack.back().second >= a % b))){
            a += stack.back().first;
            b += stack.back().second;
            stack.pop_back();
        }
        stack.emplace_back(a, b);
    }
    long double ans{};
    for(const auto& [a, b] : stack)ans += a < b ? a + b : 2 * sqrt(static_cast<long double>(a)) * sqrt(static_cast<long double>(b));
    cout << fixed << setprecision(30) << ans << endl;
    return 0;
}