import Data.List
import qualified Data.Map as Map

f ::[(Char,Int)]->[(Char,Int)]
f c@(('A',_):('B',_):[])=c
f (('A',a):[])=(('A',a):('B',0):[])
f (('B',b):[])=(('A',0):('B',b):[])

main =do
      t<-getLine
      u<-getLine
      l<-getLine
      let xs=group $ sort u
          ys=group $ sort l
          zs1=f $ zip (map head xs) (map length xs)
          zs2=f $ zip (map head ys) (map length ys)
          ms=Map.fromListWith min (zs1++zs2)
      print $ sum(Map.elems ms)