using System;
using System.Linq;
using System.Collections.Generic;
using System.Text;
using static System.Console;
using static System.Math;

class Program
{
    static void Main(string[] args)
    {
        solve();
    }
    static Scanner cin;

    static int N;
    static int[] a;
    static void input()
    {
        cin = new Scanner();
        N = cin.nextInt();
        a = cin.ArrayInt(N);
    }
    static void solve()
    {
        input();
        Dictionary<int, int> dic = new Dictionary<int, int>();
        if (N % 2 == 1)
            dic.Add(0, 1);
        for(int i = 0; i < N; i++)
        {
            int A = a[i];
            if (dic.ContainsKey(A))
            {
                dic[A]++;
            }
            else
            {
                dic.Add(A, 1);
            }
            if(dic[A] == 3)
            {
                WriteLine(0);
                return;
            }
        }
        Mod mod = new Mod(1000000007);
        WriteLine(mod.Pow(2, N / 2));
    }

    
    class Scanner
    {
        string[] s;
        int i;

        char[] cs = new char[] { ' ' };

        public Scanner()
        {
            s = new string[0];
            i = 0;
        }
        
        public string next()
        {
            if (i < s.Length) return s[i++];
            string st = Console.ReadLine();
            while (st == "") st = Console.ReadLine();
            s = st.Split(cs, StringSplitOptions.RemoveEmptyEntries);
            if (s.Length == 0) return next();
            i = 0;
            return s[i++];
        }

        public int nextInt()
        {
            return int.Parse(next());
        }

        public int[] ArrayInt(int N, int add = 0)
        {
            int[] Array = new int[N];
            for(int i = 0; i < N; i++)
            {
                Array[i] = nextInt() + add;
            }
            return Array;
        }

        public long nextLong()
        {
            return long.Parse(next());
        }

        public long[] ArrayLong(int N, long add = 0)
        {
            long[] Array = new long[N];
            for(int i = 0; i < N; i++)
            {
                Array[i] = nextLong() + add;
            }
            return Array;
        }

        public double nextDouble()
        {
            return double.Parse(next());
        }

        public double[] ArrayDounble(int N, int add = 0)
        {
            double[] Array = new double[N];
            for (int i = 0; i < N; i++)
            {
                Array[i] = nextDouble() + add;
            }
            return Array;
        }
    }
      public class Mod
    {
        public long modulo;
        public Mod(long _module)
        {
            modulo = _module;
        }

        public long Add(long n, long m)
        {
            return (n % modulo + m % modulo) % modulo;
        }

        public long Sub(long val, long minos)
        {
            long ret = val % minos;
            if (ret < 0) ret += minos;

            return ret;
        }
        public long Mul(long a, long b)
        {
            return ((a % modulo) * (b % modulo)) % modulo;
        }
        public long Pow(long b, long i)
        {
            long ret = 1;
            while(i > 0)
            {
                if ((i & 1) > 0)
                    ret = ret * b % modulo;

                b = b * b % modulo;
                i >>= 1;
            }
            return ret;
        }
        public long Inv(long val)
        {
            return Pow(val, modulo - 2);
        }
        public long Div(long val, long by)
        {
            return (val * Inv(by)) % modulo;
        }
    }
}

Measured memory_bytes: 23520