Write a Python program function F as Fn = Fn-1 + Fn-2

Defined as a function F as Fn = Fn-1 + Fn-2. Write a Python program which accepts a value for N (where N >0) as input and pass this value to the function. Display suitable error message if the condition for input value is not followed

Program:-

def fn(n):
 if n == 1:
    return 0
 elif n == 2:
    return 1
 else:
    return fn(n-1) + fn(n-2)
num = int(input("Enter a number : "))
if num > 0:
 print("fn(", num, ") = ",fn(num) , sep ="")
else:
 print("Error in input")

Output:-

Enter a number : 5
fn(5) =3
Enter a number : -1
Error in input