problems:
52448, 52468, 52472, 52475, 52646, 52797, 52802, 52863, 52999, 53001,
53101, 53371, 53373, 53383, 53384, 53736, 53812, 53921, 55578, 55580,
55581, 55772, 55775, 56557, 57093, 57094, 58630, 60114