#include <bits/stdc++.h>
#define REP(i, n) for(int i = 0;i < n;i++)
#define REPR(i, n) for(int i = n;i >= 0;i--)
#define FOR(i, m, n) for(int i = m;i < n;i++)
#define FORR(i, m, n) for(int i = m;i >= n;i--)
#define SORT(v, n) sort(v, v+n);
#define VSORT(v) sort(v.begin(), v.end());
#define INF 999999999
#define M_PI 3.14159265358979323846
#define ALL(X) (X).begin(),(X).end()

#ifdef __LOCAL
    #define DBG(X) cout << #X << " = " << (X) << endl;
    #define SAY(X) cout << (X) << endl;
#else
    #define DBG(X)
    #define SAY(X)
#endif

#ifdef __LOCAL
    #include <filesystem>
    namespace fs = std::filesystem;
#endif

using namespace std;

using ll = long long int;
using ull = unsigned long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

int dx[]={1, 0, -1, 0, 0};
int dy[]={0, 1, 0, -1, 0};
const int INT_INF = (int)(2e9);
const ll  LL_INF = (ll)(2e18);
const int NIL = -1;
static mt19937 _g(time(nullptr));
 
std::string pad(int num){ char buffer[4]; std::snprintf(buffer, sizeof(buffer), "%03d", num); return buffer;}
inline ll randint(ll a, ll b) { ll w = (_g() << 31LL) ^ _g(); return a + w % (b - a + 1); }
inline void fast_io() { ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr); };
template<typename T> inline T sign(T x) { return T(x > 0) - T(x < 0); }
template<typename T, typename S> inline ostream& operator<<(ostream& os, const pair<T, S> p) { cout << "[" << p.first << ";" << p.second << "]"; return os; }
template<typename T, typename S> inline ostream& operator<<(ostream& os, const map<T, S> p) { for (auto el : p) cout << "[" << el.first << "," << el.second << "] "; return os; }
template<typename T> inline ostream& operator<<(ostream& os, const vector<T>& v) { for (auto el : v) cout << el << " "; return os; }
template<typename T> inline T fetch() { T ret; cin >> ret; return ret; }
template<typename T> inline vector<T> fetch_vec(int sz) { vector<T> ret(sz); for (auto& elem : ret) cin >> elem; return ret; }

ll N;
vector<ll> A;
const ll MOD = (ll)(1e9+7);

void input(){
    #ifdef __LOCAL
        fs::path path_to_file = __FILE__;
        fs::path input,output;
        input = output = path_to_file.parent_path();
        input += string("/input/") + string(path_to_file.stem()) + string(".txt");
        output += string("/output/") + string(path_to_file.stem()) + string(".txt");
        freopen(input.c_str(), "r", stdin);
        freopen(output.c_str(), "w", stdout);
    #endif
    cin >> N;
    REP(i,N){
        ll a;
        cin >> a;
        A.push_back(a);
    }
    VSORT(A)
}

bool isValid(vector<ll> a){
    bool ans=true;
    if(N%2==1){
        ans &= (a[0]==0);
        for(int i=1;i<=((N-1)/2);i++){
            ans &= (a[2*i-1]==2*i);
            ans &= (a[2*i]==2*i);
        }

    }
    else{
        for(int i=0;i<N/2;i++){
            ans &= (a[2*i]==2*i+1);
            ans &= (a[2*i+1]==2*i+1);
        }
    }
    return ans;
}

ll mod_pow(ll a, ll b){
    ll res=1LL;
    while(b>0){
        if(b&1) res = (res*a)%MOD;
        a=(a*a)%MOD;
        b=(b>>1);
    }
    return res;
}

int solve(){
    if(!isValid(A)) {
        cout << 0 << endl;
        return 0;
        }
    ll ans = (N%2==0) ? mod_pow(2LL,N/2) : mod_pow(2LL,(N-1)/2);
    cout << ans << endl;
    return 0;
}

int main(){
    input();
    solve();
    return 0;
}


Measured memory_bytes: 1908