Valid Sequence Checker

In this problem, you are given a sequence consisting only of characters A and B. Your task is to determine whether the sequence is valid.

A sequence is considered valid if it does not contain any adjacent B characters. In other words, for every index \(i\) (with \(1 \le i < n\)), if \(s_i = \text{B}\) then \(s_{i+1} \neq \text{B}\). This condition can be expressed in \(\LaTeX\) as:

$$\forall\, i \in [1, n-1], \quad \text{if } s_i = \text{B} \text{ then } s_{i+1} \neq \text{B}.$$

Output VALID if the sequence satisfies the condition, otherwise output INVALID.

inputFormat

The input is read from stdin and consists of a single line containing a non-empty string. The string contains only the characters A and B.

outputFormat

Output VALID if the sequence is valid (i.e. it does not contain two consecutive B's), otherwise output INVALID.

The output should be written to stdout.

## sample

AABAB

VALID

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