#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <array>
#include <queue>
#include <deque>
#include <map>
#include <set>
#include <sstream>
#include <stdio.h>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <list>
#include <numeric>
#include <stack>
#include <iomanip>
#include <random>
#include <complex>
#include <functional>

using namespace std;

#define Rep(i,a,b) for(int i = a; i < b; ++i)
#define rep(i,b) Rep(i,0,b)
#define allof(a) (a).begin(), (a).end()

#define Yes(q) ((q) ? "Yes" : "No")
#define YES(q) ((q) ? "YES" : "NO")
#define Possible(q) ((q) ? "Possible" : "Impossible")
#define POSSIBLE(q) ((q) ? "POSSIBLE" : "IMPOSSIBLE")

using ll =  long long;

using pint = std::pair<int, int>;
using pll = std::pair<ll, ll>;


constexpr int inf = 1e9 + 7;
constexpr ll infll = 1ll << 60ll;
constexpr ll mod = 1e9 + 7;
// 0~3までは右左下上 4~7までは斜め
constexpr int dx[] = { 1, 0, -1, 0, 1, 1, -1, -1 };
constexpr int dy[] = { 0, -1, 0, 1, 1, -1, -1, 1 };

namespace { 
	template<typename T> void chmax(T& a, T b) { a = std::max(a, b); }
	template<typename T> void chmin(T& a, T b) { a = std::min(a, b); }
	template<typename T> void chadd(T& a, T b) { a = a + b; }
	template<typename T> T gcd(T a, T b) { if (a < b) std::swap(a, b); while (b) std::swap(a %= b, b); return a; }
	template<typename T> T lcm(const T a, const T b) { return a / gcd(a, b) * b; }

	template <typename T> void Dump(T& x, char end = '\n') { std::cout << x << end; }
	template <typename T> void DUmp(std::vector<T>& x, char sep = ' ', char end = '\n') { for (std::size_t i = 0, sz = x.size(); i < sz; i++) { std::cout << x[i] << (i == sz - 1 ? end : sep); } }


	// 標準入出力
	struct inp {
		size_t sz;
		inp(size_t _sz = 1) : sz(_sz) {}
		template <typename T> operator T () const { T a; std::cin >> a; return a; }
		template <typename T> operator std::vector<T>() const { vector<T> a(sz); for (std::size_t i = 0; i < sz; i++) std::cin >> a[i]; return a; }
		template <typename T, typename U> operator std::pair<T, U>() const { T f; U s; std::cin >> f >> s; return std::pair<T, U>(f, s); }
	};

	inp inp1; // input one

		// これを使うことで，(a % mod) / b の計算などができる
	template<int MOD> struct Fp {
		long long val;
		constexpr Fp(long long v = 0) noexcept : val(v% MOD) {
			if (val < 0) val += MOD;
		}
		constexpr int getmod() { return MOD; }
		constexpr Fp operator - () const noexcept {
			return val ? MOD - val : 0;
		}
		constexpr Fp operator + (const Fp& r) const noexcept { return Fp(*this) += r; }
		constexpr Fp operator - (const Fp& r) const noexcept { return Fp(*this) -= r; }
		constexpr Fp operator * (const Fp& r) const noexcept { return Fp(*this) *= r; }
		constexpr Fp operator / (const Fp& r) const noexcept { return Fp(*this) /= r; }
		constexpr Fp& operator += (const Fp& r) noexcept {
			val += r.val;
			if (val >= MOD) val -= MOD;
			return *this;
		}
		constexpr Fp& operator -= (const Fp& r) noexcept {
			val -= r.val;
			if (val < 0) val += MOD;
			return *this;
		}
		constexpr Fp& operator *= (const Fp& r) noexcept {
			val = val * r.val % MOD;
			return *this;
		}
		constexpr Fp& operator /= (const Fp& r) noexcept {
			long long a = r.val, b = MOD, u = 1, v = 0;
			while (b) {
				long long t = a / b;
				a -= t * b; std::swap(a, b);
				u -= t * v; std::swap(u, v);
			}
			val = val * u % MOD;
			if (val < 0) val += MOD;
			return *this;
		}
		constexpr bool operator == (const Fp& r) const noexcept {
			return this->val == r.val;
		}
		constexpr bool operator != (const Fp& r) const noexcept {
			return this->val != r.val;
		}
		friend constexpr std::ostream& operator << (std::ostream& os, const Fp<MOD>& x) noexcept {
			return os << x.val;
		}
		friend constexpr Fp<MOD> modpow(const Fp<MOD>& a, long long n) noexcept {
			if (n == 0) return 1;
			auto t = modpow(a, n / 2);
			t = t * t;
			if (n & 1) t = t * a;
			return t;
		}
	};
	using mint = Fp<mod>;

	ll powll(ll a, ll n) {
		ll result = 1;
		ll base = a;
		ll mask = 1;
		while (mask <= n) {
			if (n & mask) (result *= base) %= mod;
			mask <<= 1;
			(base *= base) %= mod;
		}
		return result;
	}
}


int main() {

	int n = inp1;
	vector<int> a = inp(n);

	mint ans = 0;

	// 間違っているかの判定
	bool impossible = false;
	sort(allof(a));
	int start = (n % 2 == 1) ? 0 : 1;
	if (start == 0) {
		if (a[0] != 0) {
			impossible = true;
		}
		start += 2;
		int cnt = 0;
		Rep(i, 1, n) {
			if (a[i] != start) impossible = true;
			if (++cnt % 2 == 0) {
				start += 2;
			}
		}
	}
	else {
		int cnt = 0;
		Rep(i, 0, n) {
			if (a[i] != start) impossible = true;
			if (++cnt % 2 == 0) {
				start += 2;
			}
		}
	}
	if (impossible) {
		cout << 0 << endl;
		return 0;
	}

	// その人がいた場所は二通りしかない
	int num = n / 2;

	ans = powll(2, num);

	Dump(ans);


	return 0;
}

Measured memory_bytes: 640