n = gets.to_i
s = gets.chomp

s.length.times do |i|
  if n > 0
    n.times do
      if s[i] == "z"
        s[i] = "a"
      elsif s[i] == "Z"
        s[i] = "A"
      else
        s[i] = s[i].succ
      end
    end
  end
end

puts s