1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
#include <iostream>

using namespace std;

const int P=1000000007;

int main()
{
    ios_base::sync_with_stdio(false);

    int n;
    cin>>n;

    bool np=false;
    int wyn=-1;

    for (int i=0; i<n; ++i)
    {
        int a;
        cin>>a;
        if (a%2)
            np=!np;
        if (np)
            continue;

        if (wyn==-1)
            wyn=1;
        else
        {
            wyn*=2;
            if (P<=wyn)
                wyn-=P;
        }
    }

    cout<<(np ? 0 : wyn)<<endl;
    return 0;
}