Problem

At Stripe, you need a reliable evaluator for arithmetic expressions used in internal rule configs. Given a string s representing a valid expression, compute its integer result.

Specification

• Input: s: str containing digits, spaces, operators + - * /, and parentheses ( ).
• Output: int value of the expression.
• Operator precedence: * and / before + and -.
• Parentheses override precedence.
• Unary +/- may appear at the start or immediately after (.
• Division truncates toward zero.

Examples

1. s = "2*(3+4)" → 14

   • (3+4)=7, then 2*7=14.

2. s = " 14 - (6/2 + 3) * 2 " → 2

   • 6/2=3, (3+3)=6, 6*2=12, 14-12=2.

3. s = "(1-4)/2" → -1

   • (1-4)=-3, -3/2 truncates toward zero → -1.

Constraints

• 1 <= len(s) <= 200000
• Expression is valid
• Intermediate results fit in 32-bit signed integer