Factorial of a number

Factorial of a number

Factorial of any number n is represented by n! which is equal to 1*2*3*….*(n-1)*n.

E.g.:
4! = 1*2*3*4 = 24
3! = 3*2*1 = 6
2! = 2*1 = 2
Also,
1! = 1
0! = 1

Write a Python program to calculate factorial of any given number.  If you enter a negative number, display “Factorial does not exist for negative numbers” and stop the program. 

Sample Input 1:

Enter a number

5

Sample Output 1:

Factorial is 120

Sample Input 2:

Enter a number

0

Sample Output 2:

Factorial is 1

Sample Input 3:

Enter a number

-5

Sample Output 3:Factorial does not exist for negative numbers

Code :-

n=int(input("Enter a number\n"))
f=1
if n<0:
    print("Factorial does not exist for negative numbers")
    exit()
elif n==0:
    print("Factorial is 1")
    exit()
else:
    for i in range(1,n+1):
        f=f*i
    print("Factorial is "+str(f))