Fig. 5. An example of computing the score of a walk p (solid) relative to a carrying path p_a = q₁q₂q₃ (dashed).

The path p forms a chain with the subpath q₂ of p_a, while subpaths q₁ and q₃ form hanging ends. We count the length of p and subtract lengths of the hanging ends. Thus, the score f(p_a, p) = 4 − (1 + 1)² = 0.