Compute Decimal Equivalent of a Fraction

You are given a fraction in the form $N/D$, where $N$ and $D$ are integers and $D \neq 0$. Your task is to compute the decimal equivalent of the fraction rounded to four decimal places. If the denominator is zero or the input string does not represent a valid fraction, output None. Note that the fraction may be negative, and the negative sign can appear in the numerator, the denominator, or both.

For example, for an input of 3/4, the output should be 0.7500; for 10/3, it should be 3.3333; and for 2/0 or an invalid string like not a fraction, the output should be None.

You must read the input from standard input (stdin) and write the result to standard output (stdout).

inputFormat

The input consists of a single line containing a fraction in the format N/D. Here, N and D are integers. There are no extra spaces in the input.

outputFormat

Output a single line containing either the decimal equivalent of the fraction rounded to four decimal places or None if the fraction is invalid or if the denominator is zero.## sample

3/4

0.7500