import sys
for s in sys.stdin:
    s = list(map(str,s))
    for i in range(len(s)):
        s[i] = ord(s[i])
        s[i] = s[i]-7
        s[i] = chr(s[i])
    
    print(''.join(s))

只要把加密過的字元先轉成ASCII碼，然後把ASCII碼加上K，再轉回字元就完成了，非常簡單:D