Canal Lock Passage Order Check

A canal lock keeper logs the direction of every vessel that passes through during a shift, writing one character per vessel in the order they passed: u for a vessel heading upstream, d for a vessel heading downstream. The lock's operating rule requires that, within any single shift, every upstream passage be logged before any downstream passage — once the first downstream passage is logged, no upstream passage may be logged afterward.

Given a shift's log, determine whether it obeys this rule.

Input format

A single line containing the shift log: a nonempty string made up only of the characters u and d.

Output format

Print true if no u appears anywhere after a d in the log (equivalently, the log consists of some number of u characters followed by some number of d characters), and false otherwise.

Constraints

• 1 <= length of the log <= 100
• Every character of the log is either u or d.

uuuddd

true

uduu

false