erlang, 129 bytes

Result

AC

Duration

1805ms

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+1end rem 51,f(Y,if X<1->"@";0<1->C end).

stdin

                        T                         
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                     K                            

stdout

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

stderr

strace