java, 173 bytes

Result

WA

Duration

1805ms

Code [DL]

class Main{public static void main(String[]a)throws Exception{int d=1,c;while((c=System.in.read())>0){if(c>83)d=0;d-=c%2*51;System.out.print(d<1?"A":(char)c+"");d=++d%51;}}}

stdin

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               K                                  

stdout

stderr

Error: Could not find or load main class A
Caused by: java.lang.ClassNotFoundException: A
rm: can't remove '/tmp/A.class': No such file or directory

strace