Corridor Motion Single Burst Audit

A building's security office places a motion sensor in a long corridor overnight. Every minute the sensor logs a 1 if it detected movement during that minute or a 0 if the corridor was empty, producing one long binary string for the whole night. A single visitor walking through produces one uninterrupted burst of 1s, and the security office is comfortable with that pattern. If the log shows two or more separate bursts of 1s -- each burst separated from the next by at least one 0 -- that suggests multiple, possibly unrelated movement events and should be flagged for review.

Given the night's log, determine whether it contains at most one contiguous burst of 1 characters.

Input format

A single line containing the binary string s, made up only of the characters 0 and 1.

Output format

Print true if s contains at most one contiguous block of 1s (including the case of no 1s at all), otherwise print false.

Constraints

1 <= length of s <= 100000 s consists only of the characters '0' and '1'.

0110

true

0110110

false