#include <bits/stdc++.h>
#ifdef LOCAL
#include "debug.h"
#define dump(...)                                                    \
    cout << "   " << string(#__VA_ARGS__) << ": "                    \
         << "[" << to_string(__LINE__) << ":" << __FUNCTION__ << "]" \
         << endl                                                     \
         << "   ",                                                   \
        dump_func(__VA_ARGS__)
#else
#define dump(...)
#endif

#define ll long long
#define int ll
#define BUF 1e5
#define INF 1 << 30
#define vi vector<int>
#define vvi vector<vector<int>>
#define all(a) (a).begin(), (a).end()
constexpr ll mod = 1e9 + 7;
using namespace std;
ll A, B, C, D, G, H, N, M, L, K, P, Q, R, W, X, Y, Z;
string S, T;
//ll ans = 0;

template <ll mod>
class Fp {
public:
    ll val;

private:
    inline void calc_mod(ll &v) {
        if (v >= mod)
            v -= mod;
    }

public:
    Fp() {}
    Fp(ll v) : val(v % mod) {
        if (val < 0)
            val += mod;
    }
    Fp operator+=(const Fp &in) {
        val += in.val;
        calc_mod(val);
        return *this;
    }
    Fp operator+(const Fp &in) const {
        return Fp(*this) += in;
    }
    Fp &operator-=(const Fp &in) {
        val -= in.val;
        calc_mod(val);
        if (val < 0)
            val += mod;
        return *this;
    }
    Fp operator-(const Fp &in) const {
        return Fp(*this) -= in;
    }
    Fp &operator*=(const Fp &in) {
        val = val * in.val % mod;
        return *this;
    }
    Fp operator*(const Fp &in) const {
        return Fp(*this) *= in;
    }
    Fp &operator/=(const Fp &in) {
        *this *= modpow(in, mod - 2);
        return *this;
    }
    Fp operator/(const Fp &in) const {
        return Fp(*this) /= in;
    }
    bool operator==(const Fp &in) const {
        return val == in.val;
    }
    bool operator!=(const Fp &in) const {
        return val != in.val;
    }
    friend Fp modpow(const Fp &in, ll n) {
        if (n == 0)
            return 1;
        if (n & 1) {
            return in * modpow(in * in, n / 2);
        } else {
            return modpow(in * in, n / 2);
        }
    }
    friend istream &operator>>(istream &is, Fp<mod> &fp) {
        is >> fp.val;
        return is;
    }

    friend ostream &operator<<(ostream &os, Fp<mod> &fp) {
        os << fp.val;
        return os;
    }
};
using modll = Fp<mod>;
class Factorial {
public:
    vector<modll> fact, finv;
    Factorial(ll n) : fact(n + 1, modll(1)), finv(n + 1, modll(1)) {
        for (int i = 2; i <= n; i++) {
            modll tmp(i);
            fact[i] = fact[i - 1] * tmp;
            finv[i] = finv[i - 1] / tmp;
        }
    }
    modll com(const ll &n, const ll &k) {
        if (n < k || n < 0 || k < 0)
            return modll(0);
        return fact[n] * finv[k] * finv[n - k];
    }
};

signed main() {
    cin >> N;
    vi a(N);
    for (int i = 0; i < N; i++) {
        cin >> a[i];
    }
    sort(all(a));
    bool flag = 0;
    if (N % 2 == 0) {
        for (int i = 0; i < N; i += 2) {
            if (a[i] != a[i + 1]) {
                flag = 1;
                break;
            }
        }
    } else {
        if (a[0] != 0)
            flag = 1;
        for (int i = 1; i < N; i += 2) {
            if (a[i] != a[i + 1]) {
                flag = 1;
                break;
            }
        }
    }
    if (flag)
        cout << 0 << endl;
    else
        cout << modpow(modll(2), N / 2).val << endl;
}


Measured memory_bytes: 1024