#include <iostream>
#include <string>
#include <algorithm>
#include <functional>
#include <vector>
#include <stack>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <cstdio>
#include <cmath>
#include <tuple>
#include <iomanip>
#include <numeric>
#include <unordered_map>
#include <sstream>   
#include<limits.h>
#include<float.h>
#include<list>
#include <array>
#include <complex>
using namespace std;
#define i64  long long
#define int  long long
 
#define I32_MAX 2147483647
#define I64_MAX 9223372036854775807LL
#define I64_MAX2 1223372036854775807LL
#define INF I64_MAX2
#define MOD 1000000007
#define MEM_SIZE 10000
#define DEBUG_OUT true

// int DP[MEM_SIZE][MEM_SIZE] = {0};
// int GMEM[MEM_SIZE][MEM_SIZE] = {0};
template<typename T> void DEBUG(T e){if(DEBUG_OUT == false)return;std::cout << e << std::endl;}
template<class T> void DEBUG(string str, T e){if(DEBUG_OUT == false)return;std::cout <<str << ">>" << e << std::endl;}
template<typename T> void DEBUG(const std::vector<T>& v){if(DEBUG_OUT == false)return;for(const auto& e : v){ std::cout << e << " "; } std::cout << std::endl;}
template<typename T> void DEBUG(const std::vector<std::vector<T> >& vv){if(DEBUG_OUT == 1)return;for(const auto& v : vv){ DEBUG(v); } }
template <class T> void corner(bool flg, T hoge) {if (flg) {cout << hoge << endl; exit(0);}}
template< typename T1, typename T2 > inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }
template< typename T1, typename T2 > inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }
template<typename T> void SORT_(std::vector<T>& v,bool GREATER = 0){if(GREATER == 0)sort(v.begin(),v.end());else{sort(v.begin(),v.end(),std::greater<T>());}}

struct mint {
  int x; // typedef long long int;
  mint(int x=0):x((x%MOD+MOD)%MOD){}
  mint& operator+=(const mint a) {
    if ((x += a.x) >= MOD) x -= MOD;
    return *this;
  }
  mint& operator-=(const mint a) {
    if ((x += MOD-a.x) >= MOD) x -= MOD;
    return *this;
  }
  mint& operator*=(const mint a) {
    (x *= a.x) %= MOD;
    return *this;
  }
  mint operator+(const mint a) const {
    mint res(*this);
    return res+=a;
  }
  mint operator-(const mint a) const {
    mint res(*this);
    return res-=a;
  }
  mint operator*(const mint a) const {
    mint res(*this);
    return res*=a;
  }
  mint pow(int t) const {
    if (!t) return 1;
    mint a = pow(t>>1);
    a *= a;
    if (t&1) a *= *this;
    return a;
  }
 
  // for prime MOD
  mint inv() const {
    return pow(MOD-2);
  }
  mint& operator/=(const mint a) {
    return (*this) *= a.inv();
  }
  mint operator/(const mint a) const {
    mint res(*this);
    return res/=a;
  }
};
 
 
void solve(void)
{
  int N;
  cin>>N;
  vector<int> data(N);
  for (int i = 0; i < N; i++)
  {
    cin>>data[i];
  }

  sort(data.begin(),data.end());

  int P =N%2;
  mint ANS;

  if(P == 0)
  {
    bool check = 1;
    for (int i = 0; i < N; i++)
    {
      if(data[i] != ((i/2)*2 + 1)) check = 0;
    } 
    if(check == true)
    {
      // cout<<(int)pow(2,N/2);
      ANS.x = 2;
      ANS = ANS.pow(N/2);
      cout<<ANS.x<<endl;
    }
    else
    {
      cout<<0<<endl;
    }
    
    
  }
  else
  {
    bool check = 1;
    for (int i = 0; i < N; i++)
    {
      if(data[i] != ((i+1)/2)*2)check = 0;
    }

    if(check == true)
    {
      ANS.x = 2;
      ANS = ANS.pow(N/2);
      cout<<ANS.x<<endl;
    }
    else
    {
      cout<<0<<endl;
    }
    
    
  }
  
  
  
  return;
}


int32_t main(int32_t argc, const char *argv[])
{
  std::ios::sync_with_stdio(false);
  std::cin.tie(0);

  std::cout << std::fixed;
  std::cout << std::setprecision(9);
  solve();

 
  return 0;
}

Measured memory_bytes: 1024