php, 105 bytes

Result

AC

Duration

722ms

Code [DL]

<?php
$b=0;$d=1;while($c=fread(STDIN,1)){$d*=$c!='T';$b=$c=='K'||$b&&$d;echo!$d||$b?'A':$c;$d=($d+1)%51;}

stdin

                                               T  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
              K                                   

stdout

                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
                                               A  
              AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA  

stderr

strace