Eulerian and Hamiltonian Graphs · Easy problem

A graph $G$ has vertices $1,\ldots,6$: a triangle on $1,2,3$ (edges $12,23,31$), a separate triangle on $4,5,6$ (edges $45,56,64$), and one edge $36$ joining the two triangles. $G$ has an Euler trail but no Euler circuit. Find the product of the two vertices between which that trail must run.