Author:  ACM ICPC 20072008, Northeastern European Regional Contest  Time limit:  3 sec  
Input file:  equation.in  Memory limit:  64 Mb  
Output file:  equation.out 
Your task is to solve an equation of the form f(x) = 0 where f(x) is written in postfix notation with numbers, operations + , − , * , / , and at most one occurrence of a variable x. For example, f(x) for an equation (4x + 2) / 2 = 0 is written as: 4X * 2 + 2 /
The solution for f(x) = 0 is x = − 1 / 2.
The input file consists of a single line with at most 30 tokens separated by spaces.
Each token is either:
The input file contains a correct representation of f(x) in postfix notation where token X occurs at most once. There is no division by a constant zero in this equation, that is, there always exists a value of x, such that f(x) can be evaluated without division by zero.
Write to the output file:
No.  Input file (equation.in ) 
Output file (equation.out ) 

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