Write a program that prompts the user to input a number and prints its factorial.

The factorial of an integer n is defined as

n! = 1 x 2 x 3 x ... x n; if n > 0

= 1; if n = 0

For instance, 6! can be calculated as 1 x 2 x 3 x 4 x 5 x 6.

```
#include <stdio.h>
int main()
{
int i, n, fact = 1;
printf("Enter a number :");
scanf("%d", &n);
for (i = 1; i <= n; i++)
{
fact *= i;
}
printf("The factorial of %d is %d.", n, fact);
return 0;
}
```

Enter a number :6

The factorial of 6 is 720.