import sys

n = int(input())
s = input()
# print(s)
#ord()获取字符ASCII
#chr()将ASCII转换为字符
# print(ord("a"))  97
# print(ord("z"))  122

for i in range(len(s)):
    #防止超出26个小写英文字母
    print(chr((n+ord(s[i])-97)%26+97),end='')