Each letter in the world is replaced by the letter which occupies the same position form the other end of the English alphabetic series, to obtain the code.
As M is 13th from the front, so in code N is 13th from the last.
U is 21st from the the front, so in code F is 21st from the last and so on.
Follow same for SEQUENCE to get code as HVJFVMXV.