__int64 __fastcall not_the_flag(int a1)
{
  if ( a1 == 42 )
    puts("Cipher from Bill \nSubmit without any tags\n#kdudpeh");
  else
    puts("YOUSUCK");
  return 0LL;
}

kdudpeh这个东西，根据题目提示sha1加密

import hashlib
flag='kdudpeh'
x = hashlib.sha1(flag.encode("utf8"))#md5和类似的，就讲sha1更换就行
y = x.hexdigest()
print(y)

80ee2a3fe31da904c596d993f7f1de4827c1450a

得到这个

over！