#pragma region template #include using namespace std; // clang-format off #include using namespace atcoder; using mint = static_modint<998244353>; using vm = vector; using vvm = vector; ostream& operator<<(ostream& os, const mint& v){ os << v.val(); return os; } using ll = long long; using vl = vector; using vvl = vector; using ld = long double; using vld = vector; using vvld = vector; using pll = pair; using vpll = vector; using vvpll = vector; template using V = vector; template using VV = vector>; template using VVV = vector>; using vb = vector; using vs = vector; using mll = map; using msl = map; template using heap = priority_queue; template using min_heap = priority_queue, greater>; constexpr ll inf = 3001001000100100100LL; constexpr int inf_int = 1000000009; #define endl '\n' #define _overload(_1, _2, _3, name, ...) name #define rep(...) _overload(__VA_ARGS__, _rep, _rep2,)(__VA_ARGS__) #define repc(...) _overload(__VA_ARGS__, _repc, _repc2,)(__VA_ARGS__) #define repr(...) _overload(__VA_ARGS__, _repr, _repr2,)(__VA_ARGS__) #define reprc(...) _overload(__VA_ARGS__, _reprc, _reprc2,)(__VA_ARGS__) #define _rep(i,k,n) for(ll i=(k) , i##_xxxx=(n); i < i##_xxxx; ++i) #define _repc(i,k,n) for(ll i=(k) , i##_xxxx=(n); i <=i##_xxxx; ++i) #define _repr(i,k,n) for(ll i=(n)-1, i##_xxxx=(k); i >=i##_xxxx; --i) #define _reprc(i,k,n) for(ll i=(n) , i##_xxxx=(k); i >=i##_xxxx; --i) #define _rep2(i,n) _rep(i,0,n) #define _repc2(i,n) _repc(i,1,n) #define _repr2(i,n) _repr(i,0,n) #define _reprc2(i,n) _reprc(i,1,n) #define rall(o) rbegin(o), rend(o) #define all(o) begin(o), end(o) template ll sz(const C& c) { return static_cast(c.size()); } template bool chmax(T& m, const T& v){ if (m < v){ m = v; return true; } return false; } template bool chmin(T& m, const T& v){ if (v < m){ m = v; return true; } return false; } template T udiv(const T& a, const T& b){ return (a + b - 1) / b; } template T rdiv(const T& a, const T& b){ return (a + b / 2) / b; } template string join(const T& v, const S& sep ){ stringstream ss; bool f = false; for (const auto& e : v){ if (f) ss << sep; f = true; ss << e;} return ss.str(); } template string join(const T& v, const S& sep, const U& ...args){ stringstream ss; bool f = false; for (const auto& c : v){ if (f) ss << sep; f = true; ss << join(c, args...); } return ss.str(); } template ostream& operator<<(ostream& os, const vector& seq){ os << '[' << join(seq, ",") << ']'; return os; } template ostream& operator<<(ostream& os, const vector>& seq){ os << '[' << join(seq, ",\n ") << ']'; return os; } template ostream& operator<<(ostream& os, const deque& seq){ os << '[' << join(seq, ",") << ']'; return os; } template ostream& operator<<(ostream& os, const set& seq){ os << '{' << join(seq, ",") << '}'; return os; } template ostream& operator<<(ostream& os, const unordered_set& seq){ os << '{' << join(seq, ",") << '}'; return os; } template ostream& operator<<(ostream& os, const map& seq){ os << '{'; bool f = false; for (const auto& e : seq){ if (f) os << ','; f = true; os << e.first << ":" << e.second; } os << '}'; return os; } template ostream& operator<<(ostream& os, const pair& pa){ os << '(' << pa.first << ',' << pa.second << ')'; return os; } #if LOCAL #define debug(...) _debug(__VA_ARGS__, __LINE__) #else #define debug(...) #endif void print() { std::cout << '\n'; } template void print(const S& a){ std::cout << a << '\n'; } template void _debug(const S& a){ std::cerr << "(L:" << std::setw(3) << a << ")\n"; } template void print(const S& a, const T&... args){ std::cout << a << ' '; print(args...); } template void _debug(const S& a, const T&... args){ std::cerr << a << ' '; _debug(args...); } struct setup_main { setup_main() { std::cin.tie(nullptr); std::ios::sync_with_stdio(false); std::cout << fixed << setprecision(15); } } setup_main_; // clang-format on #pragma endregion ll cnt(ll n) { // if (n == 0) return 0; ll ret = 0; while (n % 2 == 0) { ret++; n /= 2; } return ret; } void solve(ll N, vector& B) { vl c(N, 0); rep(i, N - 1) { // debug(N, i, N - 1 - i, i + 1); c[i + 1] = c[i] + cnt(N - 1 - i) - cnt(i + 1); } vl f(N); rep(i, N) f[i] = (c[i] == 0 ? 1 : 0); ll free = 0, k = 0, r = 0; rep(i, N) { if (B[i] == 1 and f[i] == 1) r++; if (B[i] == -1 and f[i] == 0) free++; if (B[i] == -1 and f[i] == 1) k++; } r %= 2; if (k == 0) { print(r == 1 ? mint(2).pow(free) : 0); return; } print(mint(2).pow(free + k - 1)); // mint S = 0, C = 1; // rep(i, k + 1) { // if (i % 2 != r) S += C; // // C_i → C_i+1 // C = C * (k - i) / (i + 1); // } // print(S * mint(2).pow(free)); } int main() { int N; cin >> N; vector B(N); rep(i, N) { cin >> B[i]; } solve(N, B); }