Figure 3

Building a new series of operations to replace $O_i{O}_{i+1}\cdots O_j$. O _i will be skipped and $O_k^{\prime }$ will mimic O _{k + 1}for k = i, i +1, ..., j -2. Finally, $O_{j-1}^{\prime }$ and O _j will be constructed according to O _j .