Prefixed expression P20006


Statement
 

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

Input

Input has a prefixed expression. This means that operators always appear before their operands. For instance, the expression 4 + 3 would be written

+ 4 3

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

* 8 + 4 3

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

* - 2 8 + 4 3

Output

Print a line with an integer number: the result of evaluating the given expression.

Hint

Note that an expression is either a digit or an operator, followed by an expression, followed by another expression. Take inspiration in this fact to write a simple recursive program.

Public test cases
  • Input

    9
    

    Output

    9
    
  • 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
    Salvador Roura
    Original language
    Catalan
    Other languages
    Catalan
    Official solutions
    C++ Java Python
    User solutions
    C++ Python