#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using namespace std;

typedef long long ll;
typedef long double ld;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef pair<int, int> pi;
typedef pair<ll, ll> pll;
typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> indexed_set;

#define imx INT_MAX
#define imn INT_MIN
#define llmx LLONG_MAX
#define llmn LLONG_MIN
#define INF         100000000000000000
#define PI          3.1415926535897932384626433832795l



#define fi first
#define se second
#define pb push_back
#define f_s(a) sort(a.begin(), a.end())
#define b_s(a) sort(a.rbegin(), a.rend())
#define p(a) cout<<a<<"\n"


// ll mod = 1000000007;
// #define l(i, )
// #define rl(i, a, b) for(int i = a; i < b; i++)






// struct mycomp {
//     bool operator() (const pair<int,int> &a, const pair<int,int> &b) const{
//         if (a.second-a.first != b.second-b.first)
//         return (a.second-a.first > b.second-b.first);
//         return a.first < b.first;
//     }
// };



/////////////////////GCD//////////////////////
ll gcd(ll a, ll b)
{
	if(b==0) return a;
	return gcd(b, a%b);
}


ll extended_gcd(ll a, ll b, ll& x, ll& y)
{
	if(b==0)
	{
		x=1;
		y=0;
		return a;
	}
	ll x1, y1;
	ll d = extended_gcd(b, a%b, x1, y1);
	x=y1;
	y=x1-y1*(a/b);
	return d;
}

////////////////////SIEVE OF ERATOSTHENES//////////////////////
vector<int> sieveoferatosthenes(int n)
{
	vector<bool> prime(n+1, true);
	for(int i = 2; i <= sqrt(n); i++)
	{
		if(prime[i])
		{
			for(int j = i*i; j<=n; j+=i)
			{
				prime[j]=false;
			}
		}
	}	
	vector<int> all_primes;
	for(int i = 2; i <=n; i++)
	{
		if(prime[i]) all_primes.pb(i);
	}
	return all_primes;
}

////////////////////BINARY EXPONENTIATION///////////////////////
ll bin_exp(ll a, ll b, ll mod)
{
	ll ans = 1;
	while(b)
	{
		if(b%2)
		{
			b--;
			ans = (ans%mod*a%mod)%mod;
		}
		b/=2;
		a = (a%mod*a%mod)%mod;
	}
	return ans;
}


///////////////////////////BFS//////////////////////////////////
void bfs(vector<int>& distance, vector<int> a[], vector<bool>& visited, int u, vector<int>& parent)
{
	visited[u]=true;
	parent[u]=-1;
	distance[u]=0;
	queue<int> q;

	q.push(u); 
    while (!q.empty()) { 
  
        int f = q.front(); 
        q.pop(); 
  		for(int i =0; i < a[f].size(); i++)
  		{
  			if(visited[a[f][i]]==false)
  			{
  				distance[a[f][i]]=distance[f]+1;
  				parent[a[f][i]]=f;
  				visited[a[f][i]]=true;
  				q.push(a[f][i]);
  			}
  		}
    } 

}

void solve()
{

}
int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);

	// #ifndef ONLINE_JUDGE
	// freopen("input.txt", "r", stdin);
	// freopen("output.txt", "w", stdout);
	// #endif
	int n;
	ll ans = 0;
	cin>>n;
	vll a(n);
	for(int i = 0; i < n; i++) 
	{
		cin>>a[i];
	}
	sort(a.begin(), a.end());
	map<ll, ll> c;
	for(int i = 0; i < n; i++)
	{
		c[a[i]]++;
	}
	if(n%2==0)
	{
		ll ct = 1, f = 0;

		for(auto i: c)
		{
			if(!(i.fi==ct and i.se==2))
			{
				f=1;
				break;
			}
			ct+=2;
		}
		if(f)
		{
			p(0);
		}
		else 
		{
			p(bin_exp(2, n/2, 1000000007));
		}
	}
	else
	{
		ll ct = 0, f = 0;

		for(auto i: c)
		{
			if(i.fi==0)
			{
				if(i.se!=1)
				{
					f=1;
					break;
				}
			}
			else 
			{
				if(!(i.fi==ct and i.se==2))
				{
					f=1;
					break;
				}
			}
			ct+=2;
		}
		if(f)
		{
			p(0);
		}
		else 
		{
			p(bin_exp(2, n/2, 1000000007));
		}
	}
	return 0;
}	

Measured memory_bytes: 4992