function
/--> int factorial(int n)
| int return
| /--< (n > 0)
| | return = 1
| \-->
| /--< (n == 0)
| | return = (n * factorial((n - 1)))
| \-->
^ return
main
int n
print "Enter a number:"
n = (input int)
print "Factorial of", n, "is", factorial(n)