A "A"?A A=0 "A=0" A  "B"?B C "C"?C   1,1,"D=B4AC=" B4ACD 1,39,D 7,1,"Top:X=B2A=" 13,16,"Y=" B2AS 7,49,S 13,49,ASBSC D0 19,1,"Root:" D=0 19,21,"Top:X=B2A=" 19,72,B2A 25,1,"X1=(BD)2A=" 25,58,(BD)2A 31,1,"X2=(BD)2A=" 31,58,(BD)2A  37,1,"]X1X2[=DA=" 37,58,DA  43,1,"X=" 49,1,"/" 43,9,B(2A) 49,19,D(4A) N G G=0 G=56 C  G=31 A  G=47G=48   N