int main() {
    int odd = 0, even = 0;
    int n; cin >> n; int a[n];
    for(int i = 0; i < n; i++) { 
        cin >> a[i];
        if(a[i]%2 == 0) even++;
        else odd++;
    }
    if(n == 1 & odd == 1) { cout << -1; return 0; }
    cout << min(odd%2, odd%2 + even%2);
    return 0;
}