Problem 114: F...... Factorials

(U.M. ACM Runoffs 2003, problem 1)

Description

The factorial of a number is defined to be the product of (i.e. multiply together) all the intgers between 1 and that number. So, for example the factorial of 5 is 1×2×3×4×5, which is 120. By definition, the factorial of zero is 1.
The symbol for factorial is an exclamation mark '!', so the above example is normally written as 5!=120.
Write a program that calculates the factorials of numbers with perfect accuracy.

Input Format

The input will consist of some number of lines; each line will contain one input number. All numbers will be non-negative except for the very last one. The last line of input will contain a negative number which is simply marks the end of the inputs; do not attempt to calculate its factorial.

Output Format

For each input, produce a single line of output. The output line should contain the input number, immedaitely followed by an '!', immediately followed by a space, immediately followed by an '=', immediately followed by a space, immediately followed by the answer.
No matter how long the answer is, print it all on one line, completely uninterrupted.

Limits

All inputs will be between 0 and 1000 inclusive

Sample Input

Sample Output

5! = 120
0! = 1
3! = 6
9! = 362880