full: search nodes 31
  used vertices 3: surfaces with boundary 4 (max dual diameter 0), closed 0 (max -1); with diam >= nv-2: 0 (max diam among orientable ones: with boundary -1, closed -1)
  used vertices 4: surfaces with boundary 10 (max dual diameter 1), closed 1 (max 1); with diam >= nv-2: 0 (max diam among orientable ones: with boundary -1, closed -1)
