Calculate the prefix
In the 1920s, the Polish mathematician Jan Lukasiewicz introduced a bracket-free way of writing algebraic expressions, now known as Polish notation. In prefix Polish notation, the operator precedes its operands. For instance, consider the infix expression (b-c/d)/(ef-(g+hk)). In prefix notation, the fragment "c/d" becomes "/cd", and "b-c/d" becomes "-b/cd". Similarly, "e*f" is "*ef", "h*k" is "*hk", and "g+h*k" is "+g*hk". Thus, "ef-(g+hk)" translates to "-ef+ghk", and the entire expression becomes "/-b/cd-ef+ghk" when considering division as the final operation.
Your task is to evaluate a given prefix expression, where operands are single-digit integers, and all operations are performed using integer arithmetic.
Constraints
The length of the expression does not exceed 150 characters.
Input
The input is a single line containing the prefix expression.
In this expression, there are no spaces, each operand is a single-digit non-negative integer, and only the binary operations "+", "-", "*", "/" are used. The tests ensure that the expression is error-free.
Output
The output should be a single line with the result of the expression, if it can be evaluated. If a division by zero occurs, output Runtime error in pos: K, where K is the position in the expression where the error happened.