"""
[13775: Virus](https://www.acmicpc.net/problem/13775)
Tier: Bronze 2
Category: 구현
"""
def solution():
key = int(input())
s = input()
for i in s:
if 'a' <= i <= 'z':
print(end=chr((ord(i) - 97 - key + 26) % 26 + 97))
key += 1
if key == 26:
key = 1
else:
print(end=i)
if __name__ == '__main__':
solution()