using System;
using System.Collections.Generic;
using System.Linq;
using static System.Console;
using static System.Convert;
using static System.Math;
//using Debug;
//using static System.Globalization.CultureInfo;
//using Edge = Pair<long, int>;
using System.Text;
class Program
{
    static void Main(string[] args)
    {
        Solve();
        //WriteLine(Solve());
    }
    static void Solve()
    {
        var num = Input.num;
        var ar = Input.ar.OrderBy(v=>v).ToArray();
        var dic = new Dictionary<int, int>();
        if (num % 2 == 0)
        {
            var t = 1;
            for (var i = 0; i < num; i++)
                if (ar[i] != t)
                { WriteLine(0); return; }
                else if (i % 2 == 1) t += 2;
            WriteLine(Modulo.Pow(2, num/2));
        }
        else
        {
            if(ar[0]!=0)
            { WriteLine(0);return; }
            var t = 2;
            for (var i = 1; i < num; i++)
                if (ar[i] != t)
                {
                    WriteLine(0); return;
                }
                else if (i % 2 == 0) t += 2;
            WriteLine(Modulo.Pow(2, num / 2));
        }
    }
}

public class Input
{
    public static string read => ReadLine().Trim();
    public static int[] ar => read.Split(' ').Select(int.Parse).ToArray();
    public static int num => ToInt32(read);
    public static long[] arL => read.Split(' ').Select(long.Parse).ToArray();
    public static long numL => ToInt64(read);
    public static char[][] gred(int h)
        => Enumerable.Repeat(0, h).Select(_ => read.ToCharArray()).ToArray();
    public static int[] ar1D(int n)
        => Enumerable.Repeat(0, n).Select(_ => num).ToArray();
    public static long[] arL1D(int n)
        => Enumerable.Repeat(0, n).Select(_ => numL).ToArray();
    public static string[] strs(int n)
        => Enumerable.Repeat(0, n).Select(_ => read).ToArray();
    public static int[][] ar2D(int n)
        => Enumerable.Repeat(0, n).Select(_ => ar).ToArray();
    public static long[][] arL2D(int n)
        => Enumerable.Repeat(0, n).Select(_ => arL).ToArray();
    public static T getValue<T>(string g)
    {
        var t = typeof(T);
        if (t == typeof(int))
            return (T)(object)int.Parse(g);
        if (t == typeof(long))
            return (T)(object)long.Parse(g);
        if (t == typeof(string))
            return (T)(object)g;
        if (t == typeof(char))
            return (T)(object)char.Parse(g);
        if (t == typeof(double))
            return (T)(object)double.Parse(g);
        if (t == typeof(bool))
            return (T)(object)bool.Parse(g);
        return default(T);
    }
    public static string[] Make<T1, T2>(out T1 v1, out T2 v2)
    {
        var r = read.Split(' ');
        v1 = getValue<T1>(r[0]);
        v2 = getValue<T2>(r[1]);
        return r;
    }
    public static string[] Make<T1, T2, T3>(out T1 v1, out T2 v2, out T3 v3)
    {
        var r = Make(out v1, out v2);
        v3 = getValue<T3>(r[2]);
        return r;
    }
    public const long Inf = (long)1e18;
    public const double eps = 1e-6;
    public const string Alfa = "abcdefghijklmnopqrstuvwxyz";
    public const int MOD = 1000000007;
}
public class Modulo
{
    private static int Multiple(int num1, int num2)
        => (int)(BigMul(num1, num2) % Input.MOD);

    public static int Pow(int m, int n)
    {
        if (n == 0) return 1;
        if (n % 2 == 0) return Pow(Multiple(m, m), n >> 1);
        else return Multiple(Pow(Multiple(m, m), n >> 1), m);
    }

    public static int Div(int a, int b)
        => Multiple(a, Pow(b, Input.MOD - 2));

    public class Combination
    {
        private int[] _fac;
        public Combination(int num)//階乗をメモ化
        {
            _fac = new int[num + 1];
            _fac[0] = 1;
            for (var i = 1; i <= num; i++)
                _fac[i] = Multiple(_fac[i - 1], i);
        }
        public int Comb(int n, int r)
        {
            if (n < r) return 0;
            if (n == r) return 1;
            var calc = _fac[n];
            calc = Div(calc, _fac[r]);
            calc = Div(calc, _fac[n - r]);
            return calc;
        }
        public int fac(int num)
            => _fac[num];
    }

}



Measured memory_bytes: 23136