651. Check If Word Is Valid After Substitutions

A string is valid if it can be produced from an empty string by repeatedly inserting the substring "abc" at any position. Given a string s of the letters a, b, c, determine whether it is valid. Return true or false. The input is JSON {s}.

Input: JSON {s}.

Output: Boolean — true or false.

Examples

Input: {"s":"aabcbc"}
Output: true
Explanation: Insert abc, then abc inside.

Input: {"s":"abcabcababcc"}
Output: true
Explanation: A valid construction exists.

Input: {"s":"abccba"}
Output: false
Explanation: Cannot be built from abc inserts.

Constraints

• 1<=|s|<=10^4
• letters a,b,c

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