main = getLine>>= \n->getLine>>=putStrLn.map(read n%)

r '?'='!'
r '!'='?'
r c=c

0%x=r x
n%'Z'=(n-1)%'A'
n%'z' = (n-1)%'a'
n%x|x>'@'&&x<'Z'||x>'`'&&x<'z'=(n-1)%succ x|True=r x