Fix the Right Answer

Create a function that takes a string and returns the right answer.

Examples

postfix("2 2 +") ➞ 4

postfix("2 2 /") ➞ 1

postfix("8 4 / 9 * 3 1 * /") ➞ 54

Notes

• The operators + - * / may be supported.
• Output always returns an integer.