  In previous papers, the author realized the following principle for many knot
theories: if a knot diagram is complicated enough then it reproduces itself,
i.e., is a subdiagram of any other diagram equivalent to it. This principle is
realized by diagram-valued invariants [ ] of knots such that [K]=K. It turns
out that in the case of free braids, the same principle can be realized an
unexpectedly easy way by a one-term invariant formula.
