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In chess, there are 6 types of pieces that can capture other pieces, and there are 5 types of pieces that can be captured. Ignoring piece color, this means that there are thirty distinct possible types of captures:
PxP
PxR
PxN
PxB
PxQ
RxP
RxR
RxN
RxB
RxQ
NxP
NxR
NxN
NxB
NxQ
BxP...