private static void insertion(Comparable[] a, int step){
        for(int i = step; i < a.length; i ++){
            Comparable temp = a[i];
            int j = i;
            while(j > 0 && less(temp, a[j - step])){
                a[j] = a[j - step];
                j -= step;
            }
            a[j] = temp;
        }
    }