Prefixed expression (2) P20006

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.