// >>> TEMPLATES #include using namespace std; using ll = long long; using ld = long double; using i32 = int32_t; using i64 = int64_t; using u32 = uint32_t; using u64 = uint64_t; #define int ll #define double ld #define rep(i,n) for (int i = 0; i < (int)(n); i++) #define rep1(i,n) for (int i = 1; i <= (int)(n); i++) #define repR(i,n) for (int i = (int)(n)-1; i >= 0; i--) #define rep1R(i,n) for (int i = (int)(n); i >= 1; i--) #define loop(i,a,B) for (int i = a; i B; i++) #define loopR(i,a,B) for (int i = a; i B; i--) #define all(x) begin(x), end(x) #define allR(x) rbegin(x), rend(x) #define rng(x,l,r) begin(x) + (l), begin(x) + (r) #define pb push_back #define eb emplace_back #define mp make_pair #define fst first #define snd second template auto constexpr inf = numeric_limits::max()/2-1; auto constexpr INF32 = inf; auto constexpr INF64 = inf; auto constexpr INF = inf; #ifdef LOCAL #include "debug.hpp" #else #define dump(...) (void)(0) #define say(x) (void)(0) #define debug if (0) #endif template struct pque : priority_queue, Comp> { vector &data() { return this->c; } void clear() { this->c.clear(); } }; template using pque_max = pque>; template using pque_min = pque>; template ::value, int> = 0> ostream& operator<<(ostream& os, T const& a) { bool f = true; for (auto const& x : a) os << (f ? "" : " ") << x, f = false; return os; } template ::value, int> = 0> ostream& operator<<(ostream& os, const T (&a)[N]) { bool f = true; for (auto const& x : a) os << (f ? "" : " ") << x, f = false; return os; } template ())), class = typename enable_if::value>::type> istream& operator>>(istream& is, T &a) { for (auto& x : a) is >> x; return is; } template ostream& operator<<(ostream& os, pair const& p) { return os << "(" << p.first << ", " << p.second << ")"; } template istream& operator>>(istream& is, pair& p) { return is >> p.first >> p.second; } struct IOSetup { IOSetup() { cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(15); } } iosetup; template struct FixPoint : private F { constexpr FixPoint(F&& f) : F(forward(f)) {} template constexpr auto operator()(T&&... x) const { return F::operator()(*this, forward(x)...); } }; struct MakeFixPoint { template constexpr auto operator|(F&& f) const { return FixPoint(forward(f)); } }; #define MFP MakeFixPoint()| #define def(name, ...) auto name = MFP [&](auto &&name, __VA_ARGS__) template struct vec_impl { using type = vector::type>; template static type make_v(size_t n, U&&... x) { return type(n, vec_impl::make_v(forward(x)...)); } }; template struct vec_impl { using type = T; static type make_v(T const& x = {}) { return x; } }; template using vec = typename vec_impl::type; template auto make_v(Args&&... args) { return vec_impl::make_v(forward(args)...); } template void quit(T const& x) { cout << x << endl; exit(0); } template constexpr bool chmin(T& x, U const& y) { if (x > y) { x = y; return true; } return false; } template constexpr bool chmax(T& x, U const& y) { if (x < y) { x = y; return true; } return false; } template constexpr auto sumof(It b, It e) { return accumulate(b, e, typename iterator_traits::value_type{}); } template int sz(T const& x) { return x.size(); } template int lbd(C const& v, T const& x) { return lower_bound(begin(v), end(v), x)-begin(v); } template int ubd(C const& v, T const& x) { return upper_bound(begin(v), end(v), x)-begin(v); } const int dx[] = { 1,0,-1,0 }; const int dy[] = { 0,1,0,-1 }; constexpr int popcnt(ll x) { return __builtin_popcountll(x); } // [a,b] template Int rand(Int a, Int b) { static mt19937_64 mt{random_device{}()}; return uniform_int_distribution(a,b)(mt); } i64 irand(i64 a, i64 b) { return rand(a,b); } u64 urand(u64 a, u64 b) { return rand(a,b); } // <<< int32_t main() { int n; cin >> n; vector a(n); cin >> a; vector pow3(n+1); pow3[0] = 1; rep (i,n) pow3[i+1] = pow3[i]*3; auto kth = [&](int s, int k) { return s/pow3[k]%3; }; vector r(n); rep (i,n) r[i] = ld(1)/a[i]; vector calc(pow3[n]); vector> dp(pow3[n]); def (solve, int s) -> pair { assert(s < pow3[n]); if (calc[s]) return dp[s]; calc[s] = true; auto &[p,q] = dp[s]; vector rest; rep (i,n) if (kth(s,i) == 0) rest.eb(i); if (rest.empty()) { int sum[3] = {}; rep (i,n) sum[kth(s,i)] += a[i]; if (sum[1] > sum[2]) p = q = 1; else p = q = 0; return {p,q}; } p = 0; rep (i,n) if (kth(s,i) == 0) { ld mi = 1; rep (j,n) if (kth(s,j) == 0) { auto val = r[i] * solve(s+pow3[i]*1).snd + (1-r[i]) * r[j] * solve(s+pow3[j]*2).fst; chmin(mi, val/(1-(1-r[i])*(1-r[j]))); } chmax(p, mi); } q = 1; rep (i,n) if (kth(s,i) == 0) { ld ma = 0; rep (j,n) if (kth(s,j) == 0) { auto val = r[i] * solve(s+pow3[i]*2).fst + (1-r[i]) * r[j] * solve(s+pow3[j]*1).snd; chmax(ma, val/(1-(1-r[i])*(1-r[j]))); } chmin(q, ma); } return {p,q}; }; auto [p,q] = solve(0); cout << p << endl; // dump(as_mat(dp)); }