We say that strings$t$ and $u$ can be interwoven into a larger string $s$ if there
is a substring $s'$ of $s$ whose symbols are formed of $t$ and $u$ as disjoint subsequences;
that is, every symbol of $s'$ must appear in $t$ or $u$, and the same symbol of $s'$ cannot
derive from both $t$ and $u$.
For example, the strings "$\color{blue}\text{ACAG}$" and "$\color{red}\text{CCG}$" can be
interwoven into "$\color{black}\text{G}\color{blue}\text{A}\color{red}\text{C}\color{blue}\text{CA}\color{red}\text{C}\color{blue}\text{G}\color{red}\text{G}\color{black}\text{TT}$".
However, they cannot be interwoven into "$\color{black}\text{G}\color{blue}\text{A}\color{red}\text{C}\color{blue}\text{CA}\color{red}\text{C}\color{black}\text{AAAA}\color{blue}\text{G}\color{red}\text{G}\color{black}\text{TT}$"
because of the appearance of the four 'A's in the middle of the subsequences.
