#include <bits/stdc++.h>
#define EPS 1e-9
#define INF 1070000000LL
#define MOD 1000000007LL
#define fir first
#define foreach(it,X) for(auto it=(X).begin();it!=(X).end();it++)
#define numa(x,a) for(auto x: a)
#define ite iterator
#define mp make_pair
#define rep(i,n) rep2(i,0,n)
#define rep2(i,m,n) for(int i=m;i<(n);i++)
#define pb push_back
#define pf push_front
#define sec second
#define sz(x) ((int)(x).size())
#define ALL( c ) (c).begin(), (c).end()
#define gcd(a,b) __gcd(a,b)
#define mem(x,n) memset(x,n,sizeof(x))
#define endl "\n"
using namespace std;
template <int POS, class TUPLE> void deploy(std::ostream &os, const TUPLE &tuple){}
template <int POS, class TUPLE, class H, class ...Ts> void deploy(std::ostream &os, const TUPLE &t){ os << (POS == 0 ? "" : ", ") << get<POS>(t); deploy<POS + 1, TUPLE, Ts...>(os, t); }
template <class T,class U> std::ostream& operator<<(std::ostream &os, std::pair<T,U> &p){ os << "(" << p.first <<", " << p.second <<")";return os; }
template <class T> std::ostream& operator<<(std::ostream &os, std::vector<T> &v){ int remain = v.size(); os << "{"; for(auto e: v) os << e << (--remain == 0 ? "}" : ", "); return os; }
template <class T> std::ostream& operator<<(std::ostream &os, std::set<T> &v){ int remain = v.size(); os << "{"; for(auto e: v) os << e << (--remain == 0 ? "}" : ", "); return os; }
template <class T, class K> std::ostream& operator<<(std::ostream &os, std::map<T, K> &mp){ int remain = mp.size(); os << "{"; for(auto e: mp) os << "(" << e.first << " -> " << e.second << ")" << (--remain == 0 ? "}" : ", "); return os; }
#define DEBUG1(var0) { std::cerr << (#var0) << "=" << (var0) << endl; }
#define DEBUG2(var0, var1) { std::cerr << (#var0) << "=" << (var0) << ", ";DEBUG1(var1); }
#define DEBUG3(var0, var1, var2) { std::cerr << (#var0) << "=" << (var0) << ", ";DEBUG2(var1,var2); }
#define DEBUG4(var0, var1, var2, var3) { std::cerr << (#var0) << "=" << (var0) << ", ";DEBUG3(var1,var2,var3); }
using ll = long long;

ll pow_mod(ll x,ll p,ll mod){//x^p % mod
  ll res = 1;
  while(p > 0){
    if(p & 1){
      res = (res * x) % mod;
    }
    x = (x * x) % mod;
    p >>= 1;
  }
  return res;
}


int main()
{
  cin.tie(0);
  ios_base::sync_with_stdio(0);
  int N;
  cin >> N;
  vector <int> nums(N);
  rep(i,N){
    cin >> nums[i];
  }
  sort(ALL(nums));
  if (N == 1) {
    if (nums[0] == 0) {
      cout << 1 << endl;
    } else {
      cout << 0 << endl;
    }
    return 0;
  }
  if (N == 2) {
    if (nums[0] == 1 && nums[1] == 1) {
      cout << 1 << endl;
    } else {
      cout << 0 << endl;
    }
    return 0;
  }
  if (N == 3) {
    if (nums[0] == 0 && nums[1] == 1 && nums[2] == 1) {
      cout << 1 << endl;
    } else {
      cout << 0 << endl;
    }
    return 0;
  }
  bool OK = true;
  if (N % 2 == 1) {
    int cur = 0;
    rep(i,sz(nums)){
      if (nums[i] != cur) {
        OK = false;
        break;
      }
      if (i % 2 == 0) {
        cur += 2;
      }
    }
  } else {
    int cur = 1;
    for (int i = 0; i < sz(nums); i+=2) {
      if (nums[i] != cur || nums[i+1] != cur) {
        OK = false;
        break;
      }
      cur += 2;
    }
  }
  if (OK) {
    cout << pow_mod(2, N / 2, MOD) << endl;
  } else {
    cout << 0 << endl;
  }
  return 0;
}



Measured memory_bytes: 640