erlang, 130 bytes

Result

AC

Duration

1584ms

Code [DL]

main(_)->f(1,"").
f(X,S)->Y=case C=io:get_chars(S,1)of"T"->1;"K"->X-50;eof->halt();_->X+1 end rem 51,f(Y,if X<1->"@";0<1->C end).

stdin

                                       T          
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                        K                         

stdout

                                       T          
                                       @          
                                       @          
                                       @          
                                       @          
                                       @          
                                       @          
                                       @          
                                       @          
                                       @          
                                       @          
                                       @          
                                       @          
                                       @          
                                       @          
                                       @          
                                       @          
                                       @          
                                       @          
                                       @          
                                       @          
                                       @          
                                       @          
                                       @          
                                       @          
                        K@@@@@@@@@@@@@@@          

stderr

strace