compare_hands(s) returns null if bad input is given
compare_hands(s) returns null if bad input is given

bfontaine/Katas,bfontaine/Katas,bfontaine/Katas,bfontaine/Katas,bfontaine/Katas,bfontaine/Katas,bfontaine/Katas,bfontaine/Katas,bfontaine/Katas,bfontaine/Katas,bfontaine/Katas,bfontaine/Katas