271. Valid Number

Given a string s, return true if s is a valid number. A valid number may have an optional sign, an integer or decimal part, and an optional exponent ('e'/'E' followed by an optional sign and an integer). Leading/trailing characters other than these make it invalid.

Input: A quoted string s.

Output: Boolean — true or false.

Examples

Input: "0"
Output: true
Explanation: Integer.

Input: "3.14"
Output: true
Explanation: Decimal.

Input: "abc"
Output: false
Explanation: Not a number.

Constraints

• 1<=s.length<=20

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