#include <bits/stdc++.h>
using namespace std;

template <int mod = (int)(1e9 + 7)>
struct ModInt {
  int x;
  ModInt() : x(0) {}
  ModInt(int64_t y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}
  ModInt &operator+=(const ModInt &p) {
    if ((x += p.x) >= mod) x -= mod;
    return *this;
  }
  ModInt &operator-=(const ModInt &p) {
    if ((x += mod - p.x) >= mod) x -= mod;
    return *this;
  }
  ModInt &operator*=(const ModInt &p) {
    x = (int)(1LL * x * p.x % mod);
    return *this;
  }
  ModInt &operator/=(const ModInt &p) {
    *this *= p.inverse();
    return *this;
  }
  ModInt operator-() const { return ModInt(-x); }
  ModInt operator+(const ModInt &p) const { return ModInt(*this) += p; }
  ModInt operator-(const ModInt &p) const { return ModInt(*this) -= p; }
  ModInt operator*(const ModInt &p) const { return ModInt(*this) *= p; }
  ModInt operator/(const ModInt &p) const { return ModInt(*this) /= p; }
  bool operator==(const ModInt &p) const { return x == p.x; }
  bool operator!=(const ModInt &p) const { return x != p.x; }
  ModInt inverse() const {
    int a = x, b = mod, u = 1, v = 0, t;
    while (b > 0) {
      t = a / b;
      swap(a -= t * b, b);
      swap(u -= t * v, v);
    }
    return ModInt(u);
  }
  ModInt pow(int64_t n) const {
    ModInt res(1), mul(x);
    while (n) {
      if (n & 1) res *= mul;
      mul *= mul;
      n >>= 1;
    }
    return res;
  }
  friend ostream &operator<<(ostream &os, const ModInt &p) { return os << p.x; }
  friend istream &operator>>(istream &is, ModInt &a) {
    int64_t t;
    is >> t;
    a = ModInt<mod>(t);
    return (is);
  }
  static int get_mod() { return mod; }
};

struct Combination {
  vector<ModInt<>> _fact, _rfact, _inv;
  Combination(long long nsize = 5000000)
      : _fact(nsize + 1), _rfact(nsize + 1), _inv(nsize + 1) {
    _fact[0] = _rfact[nsize] = _inv[0] = 1;
    for (int i = 1; i <= nsize; i++) _fact[i] = _fact[i - 1] * i;
    _rfact[nsize] /= _fact[nsize];
    for (int i = nsize - 1; i >= 0; i--) _rfact[i] = _rfact[i + 1] * (i + 1);
    for (int i = 1; i <= nsize; i++) _inv[i] = _rfact[i] * _fact[i - 1];
  }
  inline ModInt<> fact(int k) const { return _fact[k]; }

  inline ModInt<> rfact(int k) const { return _rfact[k]; }

  inline ModInt<> inv(int k) const { return _inv[k]; }

  ModInt<> P(int n, int r) const {
    if (r < 0 || n < r) return 0;
    return fact(n) * rfact(n - r);
  }

  ModInt<> C(int p, int q) const {
    if (q < 0 || p < q) return 0;
    return fact(p) * rfact(q) * rfact(p - q);
  }

  ModInt<> largeC(long long p, long long q) const {
    if (q < 0 || p < q) return 0;
    if (q >= (long long)_fact.size()) q = p - q;
    // if (q >= (long long)5000) q = p - q;
    ModInt<> res = rfact(q);
    for (int i = 0; i < q; ++i) res *= p - i;
    return res;
  }

  // n types,choose r
  ModInt<> H(int n, int r) const {
    if (n < 0 || r < 0) return (0);
    return r == 0 ? 1 : C(n + r - 1, r);
  }

  ModInt<> largeH(long long n, long long r) const {
    if (n < 0 || r < 0) return (0);
    return r == 0 ? 1 : largeC(n + r - 1, r);
  }

  ModInt<> Catalan(int n) {
    // C(2n,n) / (n + 1)
    return fact(2 * n) * rfact(n + 1) * rfact(n);
  }
};
using mint = ModInt<>;

unsigned long long popcount(unsigned long long x) {
  x = ((x & 0xaaaaaaaaaaaaaaaaUL) >> 1) + (x & 0x5555555555555555UL);
  x = ((x & 0xccccccccccccccccUL) >> 2) + (x & 0x3333333333333333UL);
  x = ((x & 0xf0f0f0f0f0f0f0f0UL) >> 4) + (x & 0x0f0f0f0f0f0f0f0fUL);
  x = ((x & 0xff00ff00ff00ff00UL) >> 8) + (x & 0x00ff00ff00ff00ffUL);
  x = ((x & 0xffff0000ffff0000UL) >> 16) + (x & 0x0000ffff0000ffffUL);
  x = ((x & 0xffffffff00000000UL) >> 32) + (x & 0x00000000ffffffffUL);
  return x;
}
// 1000 -> 3
inline int trail(unsigned long long s) { return (s ? __builtin_ctzll(s) : 64); }
// 111 -> 29
inline int lead(unsigned long long s) { return (s ? __builtin_clzll(s) : 64); }

int n;
vector<int> cnt, b;
Combination com;

mint solve();

int main() {
  cin >> n;
  b.push_back(0);
  cnt.push_back(0);
  for (int i = 0, now = 0; i < n; ++i) {
    ++now;
    int p;
    cin >> p;
    if (p >= 0) {
      cnt.push_back(now);
      b.push_back(p);
      now = 0;
    }
  }
  n = b.size();
  cout << solve() << endl;
  return 0;
}

mint solve() {
  for (int i = 1; i < n; ++i)
    if ((b[i - 1] & b[i]) != b[i - 1]) return 0;
  mint res = 1;
  for (int i = 1; i < n; ++i) {
    mint sum = 0;
    for (int nc = 0; nc <= cnt[i]; ++nc) {
      mint now = 1;
      int used = popcount(b[i - 1] & b[i]), add = popcount(b[i - 1] ^ b[i]);
      now *= mint(2).pow(nc * used);
      now *= (mint(2).pow(nc) - 1).pow(add);
      now *= com.C(cnt[i], nc);
      if ((nc ^ cnt[i]) & 1)
        sum -= now;
      else
        sum += now;
    }
    res *= sum;
  }
  return res;
}