Language: C++

#include <algorithm>
#include <string>
 
using namespace std;
 
const long mod = 1e9+7;
 
#define REP(i, n)  for(int i = 0; i < (int)n; ++i)
 
int main() {
    int N;
    int a;
    cin >> N;
    vector<int> A;
    REP(i, N) {
        cin >> a;
        A.push_back(a);
    }
    int init = 0;
    if (N % 2 == 0) {
        init = 1;
    }
    sort(A.begin(), A.end());
    for (int i = init; i <= N; i += 2) {
        if (i==0){
            if (A[0]==A[1]) {
                cout << 0 << endl;
                return 0;
            }
        } else if (i != 0) {
            if (A[i - 1] != A[i]) {
                cout << 0 << endl;
                return 0;
            }
        }
    }
    long out = 1;
    REP(i, N / 2) out = out * 2 % mod;
    cout << out << endl;
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:13:5: error: 'cin' was not declared in this scope
   13 |     cin >> N;
      |     ^~~
a.cc:3:1: note: 'std::cin' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
    2 | #include <string>
  +++ |+#include <iostream>
    3 | 
a.cc:14:5: error: 'vector' was not declared in this scope
   14 |     vector<int> A;
      |     ^~~~~~
a.cc:3:1: note: 'std::vector' is defined in header '<vector>'; this is probably fixable by adding '#include <vector>'
    2 | #include <string>
  +++ |+#include <vector>
    3 | 
a.cc:14:12: error: expected primary-expression before 'int'
   14 |     vector<int> A;
      |            ^~~
a.cc:17:9: error: 'A' was not declared in this scope
   17 |         A.push_back(a);
      |         ^
a.cc:23:10: error: 'A' was not declared in this scope
   23 |     sort(A.begin(), A.end());
      |          ^
a.cc:27:17: error: 'cout' was not declared in this scope
   27 |                 cout << 0 << endl;
      |                 ^~~~
a.cc:27:17: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:27:30: error: 'endl' was not declared in this scope
   27 |                 cout << 0 << endl;
      |                              ^~~~
a.cc:3:1: note: 'std::endl' is defined in header '<ostream>'; this is probably fixable by adding '#include <ostream>'
    2 | #include <string>
  +++ |+#include <ostream>
    3 | 
a.cc:32:17: error: 'cout' was not declared in this scope
   32 |                 cout << 0 << endl;
      |                 ^~~~
a.cc:32:17: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:32:30: error: 'endl' was not declared in this scope
   32 |                 cout << 0 << endl;
      |                              ^~~~
a.cc:32:30: note: 'std::endl' is defined in header '<ostream>'; this is probably fixable by adding '#include <ostream>'
a.cc:39:5: error: 'cout' was not declared in this scope
   39 |     cout << out << endl;
      |     ^~~~
a.cc:39:5: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:39:20: error: 'endl' was not declared in this scope
   39 |     cout << out << endl;
      |                    ^~~~
a.cc:39:20: note: 'std::endl' is defined in header '<ostream>'; this is probably fixable by adding '#include <ostream>'