ช่วยด้วยคับงานด่วน

Write a program to receive a positive integer from the keyboard, and print the factorial value of it. You
program must handle the number up to 1000!
Note that a normal integer is 32 bit, which can handle up to around 4 billion. This is not enough for
1000! You have to use an array of digits to store the result. You have to write down your own
multiplication routine for this array.