local n = tonumber(io.read())
local s = io.read()
local t = io.read()

local ans = (function ()
  local count = 0
  for i = 1, n do
    if not (s:sub(i, i) == t:sub(i, i)) then
      count = count + 1
    end
  end
  return count
end)()

print(ans)