Wolf Sothe is playing the game Delaymaster. In this game, he can create new words according to the following rules:

For each positive integer n, the string which consists of n copies of 'w', then n copies of 'o', then n copies of 'l', and finally n copies of 'f' is a valid word.

The concatenation of two valid words is a valid word.

Only the words that can be obtained by rules 1 and 2 are valid. There are no other valid words.

Thus, for example:

By rule 1, "wolf", "wwoollff", and "wwwooolllfff" are valid words.

Then, by rule 2, "wolfwwoollff" is a valid word.

By applying rule 2 twice, "wolfwwoollffwolf" is a valid word.

The string "wfol" is not a valid word (order matters).

The string "wwolfolf" is not a valid word (we can only concatenate, not insert one word into another).

The string "wwwoolllfff" is not a valid word (only two 'o's instead of three).

You are given a string str. Return "VALID" if str is a valid word and "INVALID" otherwise. Note that the return value is case-sensitive: you must return the strings "VALID" and "INVALID" in all-uppercase.