#include <bits/stdc++.h>

using namespace std;

struct Initializer {
  Initializer() {
    cin.tie(0);
    ios::sync_with_stdio(0);
    cout << fixed << setprecision(15);
  }
} initializer;

template<typename T> istream& operator>>(istream &s, vector<T> &v) {
  for (T &t : v) s >> t;
  return s;
}

template<typename T> ostream& operator<<(ostream &s, const vector<T> &v) {
  for (const T &t : v) s << t << endl;
  return s;
}

template<typename T> T min(vector<T>& v) {return *min_element(v.begin(), v.end());}

template<typename T> T max(vector<T>& v) {return *max_element(v.begin(), v.end());}

template<typename T> int min_element(vector<T>& v) {return min_element(v.begin(), v.end()) - v.begin();}

template<typename T> int max_element(vector<T>& v) {return max_element(v.begin(), v.end()) - v.begin();}

template<typename T> void sort(vector<T>& v) {sort(v.begin(), v.end());}

template<typename T, typename Function> void sort(vector<T>& v, Function func) {sort(v.begin(), v.end(), func);}

template<typename T> void rsort(vector<T>& v) {sort(v.rbegin(), v.rend());}

template<typename T> void reverse(vector<T>& v) {reverse(v.begin(), v.end());}

template<typename T> void unique(vector<T>& v) {v.erase(unique(v.begin(), v.end()), v.end());}

template<typename T> void nth_element(vector<T>& v, int n) {nth_element(v.begin(), v.begin() + n, v.end());}

template<typename T> bool next_permutation(vector<T>& v) {return next_permutation(v.begin(), v.end());}

template<typename T> int find(vector<T>& v, T t) {return find(v.begin(), v.end(), t) - v.begin();}

template<typename T> int in(vector<T> v, T t) {return find(v, t) != (int)v.size();}

template<typename T> int lower_bound(vector<T>& v, T t) {return lower_bound(v.begin(), v.end(), t) - v.begin();}

template<typename T> int upper_bound(vector<T>& v, T t) {return upper_bound(v.begin(), v.end(), t) - v.begin();}

template<typename T> T accumulate(const vector<T>& v, function<T(T, T)> func = plus<T>()) {return accumulate(v.begin(), v.end(), T(), func);}

template<typename T> void adjacent_difference(vector<T>& v) {adjacent_difference(v.begin(), v.end(), v.begin());}

template<typename T> void adjacent_difference(vector<T>& v, vector<T>& u) {adjacent_difference(v.begin(), v.end(), u.begin());}

template<typename T> void partial_sum(vector<T>& v, vector<T>& u) {partial_sum(v.begin(), v.end(), u.begin());}

template<typename T> T inner_product(vector<T>& v, vector<T>& u) {return inner_product(v.begin(), v.end(), u.begin(), T(0));}

template<typename T> int count(const vector<T>& v, T t) {return count(v.begin(), v.end(), t);}

template<typename T, typename Function> int count_if(const vector<T>& v, Function func) {return count_if(v.begin(), v.end(), func);}

template<typename T, typename Function> void remove_if(vector<T>& v, Function func) {v.erase(remove_if(v.begin(), v.end(), func), v.end());}

template<typename T, typename Function> bool any_of(vector<T> v, Function func) {return any_of(v.begin(), v.end(), func);}

template<typename T> vector<T> subvector(vector<T>& v, int a, int b) {return vector<T>(v.begin() + a, v.begin() + b);}

template<typename T> int kinds(const vector<T>& v) {return set<T>(v.begin(), v.end()).size();}

template<typename T> void iota(vector<T>& v) {iota(v.begin(), v.end(), T());}

template<typename T> bool is_sorted(const vector<T>& v) {return is_sorted(v.begin(), v.end());}

template<typename T> class Addition {
public:
  template<typename V> T operator+(const V& v) const {
    return T(static_cast<const T&>(*this)) += v;
  }
};

template<typename T> class Subtraction {
public:
  template<typename V> T operator-(const V& v) const {
    return T(static_cast<const T&>(*this)) -= v;
  }
};

template<typename T> class Multiplication {
public:
  template<typename V> T operator*(const V& v) const {
    return T(static_cast<const T&>(*this)) *= v;
  }
};

template<typename T> class Division {
public:
  template<typename V> T operator/(const V& v) const {
    return T(static_cast<const T&>(*this)) /= v;
  }
};

template<typename T> class Modulus {
public:
  template<typename V> T operator%(const V& v) const {
    return T(static_cast<const T&>(*this)) %= v;
  }
};

template<typename T> class IndivisibleArithmetic : public Addition<T>, public Subtraction<T>, public Multiplication<T> {};

template<typename T> class Arithmetic : public IndivisibleArithmetic<T>, public Division<T> {};

class Inverse {
private:
  long long mod;
  vector<long long> inv;
  
public:
  Inverse() {}
  
  Inverse(long long mod, long long n = 1000000) : mod(mod), inv(n, 1) {for (int i = 2; i < n; ++i) inv[i] = inv[mod % i] * (mod - mod / i) % mod;}
  
  long long operator()(long long a) const {
    if (a < (int)inv.size()) return inv[a];
    long long b = mod, x = 1, y = 0;
    while (b) {
      long long t = a / b;
      swap(a -= t * b, b);
      swap(x -= t * y, y);
    }
    return (x %= mod) < 0 ? x + mod : x;
  }
};

class Mint : public Arithmetic<Mint> {
private:
  static long long mod;
  static Inverse inverse;
  long long val;

public:
  Mint() : val(0) {}

  Mint(const long long& val) {
    this->val = val % mod;
    if (this->val < 0) this->val += mod;
  }

  static void setMod(const long long& m) {
    mod = m;
    inverse = Inverse(m);
  }

  Mint operator+=(const Mint& m) {
    val += m.val;
    if (val >= mod) val -= mod;
    return *this;
  }

  Mint operator-=(const Mint& m) {
    val -= m.val;
    if (val < 0) val += mod;
    return *this;
  }

  Mint operator*=(const Mint& m) {
    val *= m.val;
    val %= mod;
    return *this;
  }

  Mint operator/=(const Mint& m) {
    val *= inverse(m.val);
    val %= mod;
    return *this;
  }

  Mint operator++() {return *this += 1;}

  Mint operator--() {return *this -= 1;}

  operator long long() {return val;}

  Mint identity() const {return 1;}
};

long long Mint::mod = 1000000007;
Inverse Mint::inverse(1000000007);

ostream& operator<<(ostream& os, Mint a) {
  os << (long long)a;
  return os;
}

istream& operator>>(istream& is, Mint& a) {
  long long n;
  is >> n;
  a = n;
  return is;
}

template<typename T> T pow(const T& m, long long n) {
  if (n == 0) {
    return m.identity();
  } else if (n < 0) {
    return m.identity() / pow(m, -n);
  }
  T mm = pow(m, n / 2);
  mm *= mm;
  if (n % 2) mm *= m;
  return mm;
}

int main() {
  int n;
  cin >> n;
  vector<int> a(n);
  cin >> a;
  sort(a);
  for (int i = 0; i < n; ++i) {
    if (a[i] == (i + n % 2) / 2 * 2 + (1 - n % 2)) continue;
    cout << 0 << endl;
    return 0;
  }
  cout << pow(Mint(2), n / 2) << endl;
}


Measured memory_bytes: 8576