enter hsimp n=1
cb: 1
exit hsimp hsexp=1
doit: 1
enter hsimp n=2
cb: 2
exit hsimp hsexp=2
doit: 2
enter hsimp n=3
cb: 6
exit hsimp hsexp=6
doit: 6
enter hsimp n=4
cb: 24
exit hsimp hsexp=24
doit: 24
enter hsimp n=5
cb: 120
exit hsimp hsexp=120
doit: 120