180. Boring Strings

Codeforces

IDCF10269180

Time1000ms

Memory256MB

Difficulty—

English · Original

Formal · Original

You consider a string of text to be _boring_ if it contains only "a" characters and "b" characters. For example, "abbaba" is boring, while "abcccbabc" is not boring. Given a string, figure out whether or not it is a _boring_ string. The only line of input contains a single string $s$, not containing spaces. If $s$ is _boring_, as described above, output "YES" (no quotes). Otherwise, output "NO". ## Input The only line of input contains a single string $s$, not containing spaces. ## Output If $s$ is _boring_, as described above, output "YES" (no quotes). Otherwise, output "NO". [samples]

**Definitions** Let $ s \in \Sigma^* $ be a string over the alphabet $ \Sigma $. **Constraints** $ s $ contains no spaces. **Objective** Determine whether $ s \subseteq \{a, b\} $. If true, output "YES"; otherwise, output "NO".

API Response (JSON)

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