Retro Problems from Issue 20
377 - Leonid N. Borodatow Quartz 19, Jan-Mar 2002
8+9. Retract 37 moves, then #1 (Proca retractor)
[5B1k/4pRnN/4nRQK/5ppp/P6p/6p1/6P1/8]
378 - Paul Raican Quartz 19, Jan-Mar 2002
2+2. Add a wK, wR, wN, wP, sK for an Illegal Cluster (2 solutions)
[8/3p2pP/3B4/8/8/8/8/8]