int sansaXor(vector<int> arr) {
    const int n = arr.size();
    
    if (n % 2 == 0)
    {
        return 0;
    }
    
    int x = 0;
    
    for (int i = 0; i < n; i += 2)
    {
        x ^= arr[i];
    }
    
    return x;
}