SimpleRev

src = 'NDCLS'
v9 = 'hadow'
key1 = 'ADSFK'
key3 = 'kills'

text1 = key3 + v9       # 这里的text1相当于 text = key3 + v9
text2 = key1 + src      # 这里的text2相当于 key = key1 + src
text2 = text2.lower()   # 需要把大学字母变为小写字母

flag = ""
for i in range(0,len(text1)):
    for x in range(0,128):      # 这里用暴力求解
        if chr(x).isalpha():    # 这里要加上判断x是否是字符
            temp = (x - 39 - ord(text2[i]) + 97) % 26 + 97
            if text1[i] == chr(temp):
                flag = flag + chr(x)
                break

print("flag{"+flag+"}")