private int recur(int count) {
    if (count > 0) {
        System.out.println(count);
        return count + recur(--count); // this value will be in stack.
    }
    return count;
}

private void divide(int low, int high) {
    System.out.println("Divide => Low: "+ low +" High: "+ high);
    if (low < high) {
        int middle = (low + high) / 2;
        divide(low, middle); // {0,7},{0,3}, {0,1} ;
        divide(middle + 1, high); // {0,0};  high = 1; // 2nd divide
        combine(low, middle, high);
    }
}