Trace out the figure of an envelope without lifting the pen and without going over the same line twice:

The graph is not Eulerian:

Since there are two odd-degree vertices, an augmented Eulerian graph is constructed by joining the odd-degree vertices via a new vertex (to avoid multiple edges):

Find an Eulerian cycle in the augmented graph:

Rotate the edges of the cycle until the edges involving the vertex

become the last ones:

Show the Eulerian path:

Find the order of vertices visited along a directed cycle:

Pick the source vertex of each edge:

Find the order of vertices visited along an undirected cycle:

The path starts at a vertex of the first edge, which is not a vertex of the second edge unless the first edge is a self-loop:

Find the vertices by following the edges in order: