#include <cstdio>
#include <iostream>
#include <cstring>
#include <algorithm>
#include <sstream>
#include <vector>
#include <map>
#include <set>
#include <deque>
#include <list>
#include <stack>
#include <queue>
#include <complex>
#include <ctime>
#include<cstdlib>
#define _USE_MATH_DEFINES
#include <math.h>
#include<cmath>
#include <cstdarg> 
#include <iomanip>

#include<unordered_map>
#include<unordered_set>
//#include <arra.y>

//#define  NDEBUG
#include <assert.h>

using namespace std;

#define dprint(Exp,...) if(Exp){fprintf(stderr, __VA_ARGS__);}
#define printe(...) fprintf(stderr, __VA_ARGS__);
#define PrtExp(_Exp)  cerr<< #_Exp <<" = "<< (_Exp)
#define PrtExpN(_Exp)  cerr<< #_Exp <<" = "<< (_Exp) <<"\n"

#define SINT(n) scanf("%d",&n);
#define SINT2(n,m) scanf("%d %d",&n,&m);
#define SINT3(n,m,o) scanf("%d %d %d",&n,&m,&o);
#define SINT4(n,m,o,p) scanf("%d %d %d %d",&n,&m,&o,&p);
#define SINT5(n,m,o,p,q) scanf("%d %d %d %d %d",&n,&m,&o,&p,&q);
//#define SLL(n) scanf("%I64d",&n);
#define SLL(n) scanf("%lld",&n);
#define SLL2(n,m) scanf("%lld %lld",&n,&m);
#define SLL3(n,m,o) scanf("%lld %lld %lld",&n,&m,&o);
#define SST(s) scanf("%s",s);
#define SCH(c) scanf("%c",&c);

#define GC() getchar();

#define PINT(n) printf("%d",(int)(n));
#define PINT2(n,m) printf("%d %d",(int)(n),(int)(m));
#define PINT3(n,m,l) printf("%d %d %d",(int)(n),(int)(m),(int)(l));
//#define PLL(n) printf("%I64d",(long long)(n));
#define PLL(n) printf("%lld",(long long)(n));
#define PST(s) printf("%s",(s));
#define PCH(s) printf("%c",(s));

#define PINTN(n) printf("%d\n",(int)(n));
#define PINT2N(n,m) printf("%d %d\n",(int)(n),(int)(m));
#define PINT3N(n,m,l) printf("%d %d %d\n",(int)(n),(int)(m),(int)(l));
//#define PLLN(n) printf("%I64d\n",(long long)(n));
#define PLLN(n) printf("%lld\n",(long long)(n));
#define PSTN(s) printf("%s\n",(s));
#define PCHN(s) printf("%c\n",(s));

#define PSP() printf(" ");
#define PN() printf("\n");

#define PC(c) putchar(c);
#define CSP (' ')
#define SN ("\n")

#define rep(i,a) for(int i=0;i<a;i++)
#define reP(i,a) for(int i=0;i<=a;i++)
#define Rep(i,a) for(int i=a-1;i>=0;i--)
#define ReP(i,a) for(int i=a;i>=0;i--)

#define rEp(i,a) for(i=0;i<a;i++)
#define rEP(i,a) for(i=0;i<=a;i++)
#define REp(i,a) for(i=a-1;i>=0;i--)
#define REP(i,a) for(i=a;i>=0;i--)

#define repft(i,a,b) for(int i=a;i<b;i++)
#define repfT(i,a,b) for(int i=a;i<=b;i++)
#define Repft(i,a,b) for(int i=a-1;i>=b;i--)
#define RepfT(i,a,b) for(int i=a;i>=b;i--)

#define foreach(a,it) for(auto it = a.begin(); it != a.end(); ++it)

#define FILL(a,v) fill(begin(a),end(a), v)
#define FILL0(a) memset(a,0,sizeof(a))
#define FILL1(a) memset(a,-1,sizeof(a))

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> Pi;
typedef pair<ll, ll>   Pll;


const int INF = 0x1f1f1f1f;//522,133,279
const ll INFLL = 0x1f1f1f1f1f1f1f1fLL;//2,242,545,357,980,376,863

template <class A, class B> inline ostream& operator<<(ostream& st, const pair<A, B>& P) { return st << "(" << P.first << "," << P.second << ")"; };
template <class A, class B> inline pair<A, B> operator+(const pair<A, B>& P, const pair<A, B>& Q) { return pair<A, B>(P.first + Q.first, P.second + Q.second); };
template <class A, class B> inline pair<A, B> operator-(const pair<A, B>& P, const pair<A, B>& Q) { return pair<A, B>(P.first - Q.first, P.second - Q.second); };

ll bitcount(ll bits) {
	bits = (bits & 0x5555555555555555) + (bits >> 1 & 0x5555555555555555);
	bits = (bits & 0x3333333333333333) + (bits >> 2 & 0x3333333333333333);
	bits = (bits & 0x0f0f0f0f0f0f0f0f) + (bits >> 4 & 0x0f0f0f0f0f0f0f0f);
	bits = (bits & 0x00ff00ff00ff00ff) + (bits >> 8 & 0x00ff00ff00ff00ff);
	bits = (bits & 0x0000ffff0000ffff) + (bits >> 16 & 0x0000ffff0000ffff);
	return (bits & 0x00000000ffffffff) + (bits >> 32 & 0x00000000ffffffff);
}

struct UnionFind {
	vector<int> data;
	UnionFind(int size) : data(size, -1) { }
	bool unionSet(int x, int y) {
		x = root(x); y = root(y);
		if (x != y) {
			if (data[y] < data[x]) swap(x, y);
			data[x] += data[y]; data[y] = x;
		}
		return x != y;
	}
	bool findSet(int x, int y) {
		return root(x) == root(y);
	}
	int root(int x) {
		return data[x] < 0 ? x : data[x] = root(data[x]);
	}
	int size(int x) {
		return -data[root(x)];
	}
};



int a[100000];

int main() {



	int n;

	cin >> n;
	rep(i, n) {
		cin >> a[i];
	}
	sort(a, a + n);
	if (n % 2 == 0) {
		int j = 1;
		for (int i = 0; i < n; j+=2, i += 2) {
			if (a[i] != j || a[i + 1] != j) {
				puts("0");
				return 0;
			}
		}

	} else {
		if (a[0] != 0) {
			puts("0");
			return 0;
		}
		int j = 2;
		for (int i = 1; i < n-1; j += 2, i += 2) {
			if (a[i] != j || a[i + 1] != j) {
				puts("0");
				return 0;
			}
		}
	}


	ll ret = 1;

	for (; n > 1; n -= 2) {
		ret = (ret * 2) % (1000000007);
	}

	cout << ret << endl;



}

Measured memory_bytes: 640