You are given an array of strings tokens that represents an arithmetic expression in Reverse Polish Notation (RPN).

Evaluate the expression and return the integer result. The valid operators are +, -, *, and /. Division truncates toward zero.

Example 1:

Input: 2 1 + 3 *
Output: 9
Explanation: ((2 + 1) * 3) = 9

Example 2:

Input: 4 13 5 / +
Output: 6
Explanation: (4 + (13 / 5)) = 6

Example 3:

Input: 10 6 9 3 + -11 * / * 17 + 5 +
Output: 22

Constraints:

• 1 ≤ tokens.length ≤ 10⁴
• tokens[i] is a valid operator or an integer in the range [-200, 200].

Input format: A single line of space-separated tokens.

Output format: A single integer.