Valid Integer

Difficulty: 1000 2000 ms 128 MB

implementation strings

Is S a canonical integer literal: an optional sign, then digits with no leading zero (0 itself is fine)?

Input: one line with the candidate string S.

Output: YES or NO.

Constraints:

• 1 ≤ |S| ≤ 100

Sample Tests

-102

YES

0102

NO

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