Write a program that reads a prefix expression, and prints the result of evaluate it. The possible operators are sum, subtraction and multiplication. The operands are natural numbers between 0 and 9 (both included).

**Input**

Input is a prefix expression. It means that always appears the operator before its operands. For instance, the expression 4 + 3 would be:

+ 4 3

The expression 8 * (4 + 3) would be:

* 8 + 4 3

The expression (2 − 8) * (4 + 3) would be:

* - 2 8 + 4 3

**Output**

Your program must print an integer: the result of evaluate the expression.

**Observation**

Use recursion (not tables). Notice that an expression or is a digit, or is an operator followed by an expression followed by another expression.

Public test cases

**Input**

+ 4 3

**Output**

7

**Input**

* 8 + 4 3

**Output**

56

**Input**

* - 2 8 + 4 3

**Output**

-42

Information

- Author
- Salvador Roura
- Language
- English
- Translator
- Carlos Molina
- Original language
- Catalan
- Other languages
- Catalan
- Official solutions
- C++
- User solutions
- C++