# CaesarEncode.py
ptxt = input("请输入明文文本: ")
for p in ptxt:
    if "a" <= p <= "z":
        print(chr(ord("a")+(ord(p)-ord("a")+3)%26), end='')
    elif "A" <= p <= "Z":
            print(chr(ord("A")+(ord(p)-ord("A")+3)%26), end='')
    else:
            print(p, end='')