Figure 1

The breakpoint graph. The breakpoint graph of $\pi =(\overrightarrow{0}\overrightarrow{1}\overrightarrow{3}\overleftarrow{3}\overleftarrow{5}\overrightarrow{4}\overleftarrow{3}\overleftarrow{5}\overleftarrow{4}\overleftarrow{3}\overrightarrow{6})$. The edge (-3, +5) has a multiplicity of 2, all other edges have a multiplicity of 1. The edge (+3, +3) is a loop. The breakpoint graph consists of three components, the edge (+1, -3) is a 1-bridge, and the pair of edges (+3, +4), (-4, -5) is a 2-bridge.