#include "bits/stdc++.h"
#ifndef err
#define err(...)(void)0
#endif
using namespace std;
using ll = long long;
using ull = decltype(1ull);
template<class T>int size(T&&a) { return a.size(); }
#define REP(t,a)for(typename make_signed<decltype(a.second)>::type t=a.first,_l##t=a.second;t<_l##t;t++)
#define RREP(t,a)for(typename make_signed<decltype(a.second)>::type t=a.second-1,_l##t=a.first;t>=_l##t;t--)
template<class B>pair<int, B>make_pair(B b) { return{ 0,b }; }
#define rep(t,...)REP(t,make_pair(__VA_ARGS__))
#define rrep(t,...)RREP(t,make_pair(__VA_ARGS__))
#define all(a)begin(a),end(a)
#define rall(a)a.rbegin(),a.rend()

void Calc();
int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr); cin.exceptions(istream::failbit | istream::badbit);
  cout << fixed << setprecision(15); Calc(); cout.flush(); return 0;
}
template<class A>void amax(A&a, A b) { a = max(a, b); }
template<class A>void amin(A&a, A b) { a = min(a, b); }
struct Scanner {
  template<class A = string>A Next() { A a; cin >> a; return a; }
  template<class A = int>vector<A>Array(int n) { vector<A>a(n); for (A&i : a) cin >> i; return a; }
  string Line() const { string s; getline(cin, s); return s; }
  template<class A>Scanner&operator,(A&a) { a = Next<A>(); return *this; }
  template<class A>operator A() { return Next<A>(); }
}in;

/*---------------------------------------------------------------------*/

const ll mod = (ll)1e9 + 7;
template<ll MOD>struct Mint {
  typedef const Mint&T;
  ll x = 0;
  Mint() {}
  Mint(ll a) { x = a % MOD; if (x < 0) x += MOD; }
  Mint&operator+=(T a) { if ((x += a.x) >= MOD) x -= MOD; return *this; }
  Mint&operator-=(T a) { if ((x += MOD - a.x) >= MOD) x -= MOD; return *this; }
  Mint&operator*=(T a) { x = x * a.x % MOD; return *this; }
  Mint&operator/=(T a) { return *this *= a.Pow(MOD - 2); }
  Mint operator+(T a)const { return Mint(*this) += a; }
  Mint operator-(T a)const { return Mint(*this) -= a; }
  Mint operator*(T a)const { return Mint(*this) *= a; }
  Mint operator/(T a)const { return Mint(*this) /= a; }
  bool operator<(T a)const { return x < a.x; }
  bool operator==(T a)const { return x == a.x; }
  Mint Pow(ll k)const {
    if (k == 0) return 1;
    Mint t = Pow(k / 2);
    return t *= (k & 1) ? t * *this : t;
  }
};
template<ll MOD>istream&operator >> (istream&i, Mint<MOD>&a) { return i >> a.x; }
template<ll MOD>ostream&operator<<(ostream&o, const Mint<MOD>&a) { return o << a.x; }
typedef Mint<mod>mint;

template<ll MOD = mod>Mint<MOD> CombMod(int n, int r) {
  Mint<MOD> a = 1, b = 1;
  rep(i, r) { a *= (n - i); }
  rep(i, 2, r + 1) { b *= i; }
  err(a, b);
  return a / b;
}

void Calc() {

  int n = in;
  auto a = in.Array(n);
  const int INF = 1e9 - 1;

  a.push_back(INF);
  sort(all(a));
  int pre = a[0];
  rep(i, !(n % 2) + 1, size(a)-1) {
    err(i, a[i]);
    if (a[i] == 0) {
      if (n % 2) {
        continue;
      } else {
        cout << (0) << endl;
        return;
      }
    }
    if (a[i] != pre + 2) {
      cout << (0) << endl;
      return;
    }
    pre = a[i];
    if (a[i] == a[i + 1]) {
      i++;
    } else {
      cout << (0) << endl;
      return;
    }
  }

  mint ans = 2;
  err(n / 2);
  cout << (ans.Pow(n/2)) << endl;

}


Measured memory_bytes: 1024