#line 1 "main.cpp" /** * @title Template */ #include #include #include #include #include #include #include #line 2 "/Users/kodamankod/Desktop/cpp_programming/Library/other/range.cpp" #line 4 "/Users/kodamankod/Desktop/cpp_programming/Library/other/range.cpp" class range { struct iter { std::size_t itr; constexpr iter(std::size_t pos) noexcept: itr(pos) { } constexpr void operator ++ () noexcept { ++itr; } constexpr bool operator != (iter other) const noexcept { return itr != other.itr; } constexpr std::size_t operator * () const noexcept { return itr; } }; struct reviter { std::size_t itr; constexpr reviter(std::size_t pos) noexcept: itr(pos) { } constexpr void operator ++ () noexcept { --itr; } constexpr bool operator != (reviter other) const noexcept { return itr != other.itr; } constexpr std::size_t operator * () const noexcept { return itr; } }; const iter first, last; public: constexpr range(std::size_t first, std::size_t last) noexcept: first(first), last(std::max(first, last)) { } constexpr iter begin() const noexcept { return first; } constexpr iter end() const noexcept { return last; } constexpr reviter rbegin() const noexcept { return reviter(*last - 1); } constexpr reviter rend() const noexcept { return reviter(*first - 1); } }; /** * @title Range */ #line 2 "/Users/kodamankod/Desktop/cpp_programming/Library/algebraic/modular.cpp" #line 2 "/Users/kodamankod/Desktop/cpp_programming/Library/algebraic/mod_inv.cpp" #line 4 "/Users/kodamankod/Desktop/cpp_programming/Library/algebraic/mod_inv.cpp" #include constexpr std::pair mod_inv(int64_t a, int64_t b) { if ((a %= b) == 0) return { b, 0 }; int64_t s = b, t = (a < 0 ? a + b : a); int64_t m0 = 0, m1 = 1, tmp = 0; while (t > 0) { const auto u = s / t; s -= t * u; m0 -= m1 * u; tmp = s; s = t; t = tmp; tmp = m0; m0 = m1; m1 = tmp; } return { s, (m0 < 0 ? m0 + b / s : m0) }; } /** * @title Extended GCD */ #line 4 "/Users/kodamankod/Desktop/cpp_programming/Library/algebraic/modular.cpp" #line 8 "/Users/kodamankod/Desktop/cpp_programming/Library/algebraic/modular.cpp" #include template class modular { public: using value_type = uint32_t; using cover_type = uint64_t; static constexpr uint32_t mod() { return Modulus::mod(); } template static constexpr value_type normalize(T value_) noexcept { if (value_ < 0) { value_ = -value_; value_ %= mod(); if (value_ == 0) return 0; return mod() - value_; } return value_ % mod(); } private: value_type value; template * = nullptr> constexpr modular inverse_helper() const noexcept { return power(*this, mod() - 2); } template * = nullptr> constexpr modular inverse_helper() const noexcept { const auto tmp = mod_inv(value, mod()); assert(tmp.first == 1); return modular(tmp.second); } public: constexpr modular() noexcept : value(0) { } template explicit constexpr modular(T value_) noexcept : value(normalize(value_)) { } template explicit constexpr operator T() const noexcept { return static_cast(value); } constexpr value_type get() const noexcept { return value; } constexpr value_type &extract() noexcept { return value; } constexpr modular operator - () const noexcept { return modular(mod() - value); } constexpr modular operator ~ () const noexcept { return inverse(*this); } constexpr modular operator + (const modular &rhs) const noexcept { return modular(*this) += rhs; } constexpr modular& operator += (const modular &rhs) noexcept { if ((value += rhs.value) >= mod()) value -= mod(); return *this; } constexpr modular operator - (const modular &rhs) const noexcept { return modular(*this) -= rhs; } constexpr modular& operator -= (const modular &rhs) noexcept { if ((value += mod() - rhs.value) >= mod()) value -= mod(); return *this; } constexpr modular operator * (const modular &rhs) const noexcept { return modular(*this) *= rhs; } constexpr modular& operator *= (const modular &rhs) noexcept { value = (cover_type) value * rhs.value % mod(); return *this; } constexpr modular operator / (const modular &rhs) const noexcept { return modular(*this) /= rhs; } constexpr modular& operator /= (const modular &rhs) noexcept { return (*this) *= inverse(rhs); } constexpr bool zero() const noexcept { return value == 0; } constexpr bool operator == (const modular &rhs) const noexcept { return value == rhs.value; } constexpr bool operator != (const modular &rhs) const noexcept { return value != rhs.value; } friend std::ostream& operator << (std::ostream &stream, const modular &rhs) { return stream << rhs.value; } friend constexpr modular inverse(const modular &val) noexcept { return val.inverse_helper(); } friend constexpr modular power(modular val, cover_type exp) noexcept { modular res(1); for (; exp > 0; exp >>= 1, val *= val) if (exp & 1) res *= val; return res; } }; template struct static_modulus { static constexpr uint32_t mod() noexcept { return Mod; } static constexpr bool is_prime = IsPrime; }; template struct dynamic_modulus { static uint32_t &mod() noexcept { static uint32_t val = 0; return val; } static constexpr bool is_prime = IsPrime; }; template using mint32_t = modular>; using rmint32_t = modular>; /* * @title Modint */ #line 16 "main.cpp" using i32 = std::int32_t; using i64 = std::int64_t; using u32 = std::uint32_t; using u64 = std::uint64_t; using isize = std::ptrdiff_t; using usize = std::size_t; constexpr i32 inf32 = (u32) ~0 >> 2; constexpr i64 inf64 = (u64) ~0 >> 2; template using Vec = std::vector; using Fp = mint32_t<1000000007>; int main() { usize N; std::cin >> N; Vec A(N); for (auto &x: A) { std::cin >> x; } { u64 mul = 1; bool big = false; for (const auto x: A) { mul *= x; if (mul > (u64) 200005 * 200005) { big = true; break; } } if (big) { Fp prd(1), sum; usize l = 0; while (A[l] == 1) { l += 1; sum += Fp(1); } usize r = N; while (A[r - 1] == 1) { r -= 1; sum += Fp(1); } for (auto i: range(l, r)) { prd *= Fp(A[i]); } std::cout << prd + sum << '\n'; return 0; } } Fp ans; Vec> vec; { usize index = 0; while (index < N && A[index] == 1) { ans += Fp(1); index += 1; } while (index < N) { u64 mul = 1; while (index < N && A[index] != 1) { mul *= A[index]; index += 1; } u64 sum = 0; while (index < N && A[index] == 1) { sum += 1; index += 1; } vec.emplace_back(mul, sum); } } const auto Size = vec.size(); Vec> calc(Size, Vec(Size + 1)); for (auto i: range(0, Size)) { for (auto j: range(i + 1, Size + 1)) { calc[i][j] = 1; for (auto k: range(i, j)) { calc[i][j] *= vec[k].first; } } } Vec dp(Size + 1); for (auto i: range(0, Size)) { for (auto j: range(i + 1, Size + 1)) { dp[j] = std::max(dp[j], dp[i] + calc[i][j] + vec[j - 1].second); } } std::cout << ans + Fp(dp.back()) << '\n'; return 0; }