erlang, 131 bytes

Result

AC

Duration

2113ms

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