Factorial Computation

Given a non-negative integer n, compute its factorial defined as \( n! = n \times (n-1)! \) with the base case \( 0! = 1 \). If the input is negative, output the error message "Factorial is not defined for negative numbers".

You need to write a complete program that reads the input from stdin and writes the output to stdout. The program should be able to handle the following scenarios:

• When n is 0 or 1, the output is 1.
• When n is positive, compute and output the factorial of n.
• When n is negative, print the exact error message.

inputFormat

The input consists of a single integer n provided via standard input.

outputFormat

If n is non-negative, output the factorial of n as an integer. If n is negative, output the error message "Factorial is not defined for negative numbers".

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