Fibonacci number?

Question

css

Coursera does not make a decision.

Condition of the problem:
Given a natural number A. Determine what Fibonacci number it is, that is, print a number n such that F[n]=A
If A is not a Fibonacci number, print the number -1
-1
Examples:
Test 1
Input : 8
Program output: 6
Test 2
Input: 10
Program output: -1
Test 3
Input: 13
Program output: 7
Can't find error

n = int(input())
f = 0
res = 1
f0 = 1
i = 0
while i < n:
    res = f
    f = f0 + f
    f0 = res
    i += 1
    if n == f:
        print(i)
        break
if n < 0 or n != f:
    print(-1)
elif n == 0:
    print(0)

Answer 1

https://codepen.io/anon/pen/rXmpqG

Answer 2

Here
Must be
A after the loop, check only n==0, and the second check is not needed, in all other cases, return -1.

Answer 3

but i like this one better

def get_fib_ind(n):
    ind = 0
    a, b = 0, 1
    while b <= n:
        ind += 1
        a, b = b, a+b
        if a == n:
            return ind
    return -1
    
print(
    get_fib_ind(
        int(input())
    )
)

Answer 4

n is the number to be checked, i.e., according to condition A, which is entered by the user, and you compare it with the serial number i in the loop.
n needs to be compared with Fiebonacci numbers

Answer 5

If the number A=1 is taken as n=2 (although one is both the first and second number in the Fibonacci sequence), then:

a = int(input())
fib_1 = 0
fib_2 = 1
fib_summ = 1
n = 0
res = -1
while fib_1 <= a:
    fib_summ = fib_1 + fib_2
    fib_1 = fib_2
    fib_2 = fib_summ
    n += 1
    if fib_1 == a:
        res = n
    elif a == 0:
        res = 0
print(res)