// >>> 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 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 fst first #define snd second template auto mp(A &&a, B &&b) { return make_pair(forward(a), forward(b)); } template auto mt(T&&... x) { return make_tuple(forward(x)...); } 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,-1,0,1,-1,-1,1 }; const int dy[] = { 0,1,0,-1,1,1,-1,-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); } template void shuffle(It l, It r) { shuffle(l, r, mt19937_64(random_device{}())); } // <<< // >>> modint template class modint { static_assert(md < (1u<<31), ""); using M = modint; using i64 = int64_t; uint32_t x; public: static constexpr uint32_t mod = md; constexpr modint(i64 x = 0) : x((x%=md) < 0 ? x+md : x) { } constexpr i64 val() const { return x; } constexpr explicit operator i64() const { return x; } constexpr bool operator==(M r) const { return x == r.x; } constexpr bool operator!=(M r) const { return x != r.x; } constexpr M operator+() const { return *this; } constexpr M operator-() const { return M()-*this; } constexpr M& operator+=(M r) { x += r.x; x = (x < md ? x : x-md); return *this; } constexpr M& operator-=(M r) { x += md-r.x; x = (x < md ? x : x-md); return *this; } constexpr M& operator*=(M r) { x = (uint64_t(x)*r.x)%md; return *this; } constexpr M& operator/=(M r) { return *this *= r.inv(); } constexpr M operator+(M r) const { return M(*this) += r; } constexpr M operator-(M r) const { return M(*this) -= r; } constexpr M operator*(M r) const { return M(*this) *= r; } constexpr M operator/(M r) const { return M(*this) /= r; } friend constexpr M operator+(i64 x, M y) { return M(x)+y; } friend constexpr M operator-(i64 x, M y) { return M(x)-y; } friend constexpr M operator*(i64 x, M y) { return M(x)*y; } friend constexpr M operator/(i64 x, M y) { return M(x)/y; } constexpr M inv() const { assert(x > 0); return pow(md-2); } constexpr M pow(i64 n) const { assert(not (x == 0 && n == 0)); if (n < 0) return inv().pow(-n); M v = *this, r = 1; for (; n > 0; n >>= 1, v *= v) if (n&1) r *= v; return r; } #ifdef LOCAL friend string to_s(M r) { return to_s(r.val(), mod); } #endif friend ostream& operator<<(ostream& os, M r) { return os << r.val(); } friend istream& operator>>(istream& is, M &r) { i64 x; is >> x; r = x; return is; } }; // <<< //constexpr int64_t MOD = 998244353; constexpr int64_t MOD = 1e9+7; using mint = modint; mint sgn(int n) { return n%2 == 0 ? +1 : -1; } // >>> mod table template struct ModTable { vector fact = {1,1}, finv = {1,1}, inv = {0,1}; void calc(int n) { int old = fact.size(); if (n < old) return; fact.resize(n+1); finv.resize(n+1); inv.resize(n+1); for (uint32_t i = old; i <= n; i++) { fact[i] = uint64_t(fact[i-1])*i % mod; inv[i] = mod - uint64_t(inv[mod%i])*(mod/i) % mod; finv[i] = uint64_t(finv[i-1])*inv[i] % mod; } } }; ModTable mod_tab; modint fact(int n) { assert(0 <= n); return mod_tab.calc(n), mod_tab.fact[n]; } modint finv(int n) { assert(0 <= n); return mod_tab.calc(n), mod_tab.finv[n]; } modint C(int n, int k) { if (n < 0 || k < 0 || n < k) return 0; return fact(n)*finv(k)*finv(n-k); } modint P(int n, int k) { assert(k >= 0); assert(n >= k); return fact(n)*finv(n-k); } // <<< constexpr int mul(int x, int y) { if (x == 0 || y == 0) return 0; int sgn = 1; if (x < 0) sgn = -sgn, x = -x; if (y < 0) sgn = -sgn, y = -y; int p = (x > INF/y ? INF : x*y); if (sgn < 0) p = -p; return p; } constexpr int add(int x, int y) { x = clamp(x, -INF, +INF); y = clamp(y, -INF, +INF); return clamp(x + y, -INF, +INF); } int32_t main() { int n; cin >> n; vector a(n); cin >> a; int ones = 0; rep (_, 2) { while (a.size() and a.back() == 1) { ones++, a.pop_back(); } reverse(all(a)); } n = a.size(); if (a.empty()) quit(ones); dump(a, ones); if (accumulate(all(a), 1LL, mul) >= INF) { mint ans = 1; for (int x : a) ans *= x; ans += ones; quit(ans); } vector p(n+1, 1); rep (i, n) p[i+1] = p[i] * a[i]; dump(p); vector dp(n+1, -INF); dp[0] = 0; rep (i, n) rep1 (j, n-i) { if (chmax(dp[i+j], dp[i] + (p[i+j]/p[i]))) { dump(i, i+j, dp[i], dp[i+j], p[i+j]/p[i]); } } dump(dp); cout << dp[n] + ones << endl; }