If the top shell of a crab is visible in each image, and the crabs on the left and right are displayed in the same position and manner.
return crab ;return top shell of #1 ;return #2 that is visible ;return images of #3 ;return images ;return number of  #4 ;return number of  #5 ;return if  #6 is equal to  #7 ;return #1 on the  left ;return #1 on the  right ;return position displayed in  of #9 ;return position displayed in  of #10 ;return if  #11 is the  same as #12 ;return manner displayed in  of #9 ;return manner displayed in  of #10 ;return if  #14 is the  same as #15 ;return if  both  #13 and   #16 are true ;return if  both  #8 and   #17 are true
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