PROGRAMMING:Is he a member of the Fibonacci family?

Mathematically, Fibonacci sequence is defined recursively as follows:
F(0)=0，F(1)=1, F(n)=F(n-1)+F(n-2)（n>=2，n∈N*）
This sequence has a very important aesthetic characteristic: when n tends to infinity, the ratio of the former term to the latter term is more and more close to the golden section, that is, f (n) / F (n-1) → 1.618..., that is, the ratio of the former term to the latter term
The formation of nature is closely related to this aesthetics
After understanding this sequence, you need to be more familiar with Fibonacci sequence through programming
Given a positive integer n (n > 1), output the number of terms in the Fibonacci sequence. If it does not exist in the sequence, output - 1. Here we stipulate that the first term of the sequence is f (1) = 1, the second term f (2) = 1.
Note: it is suggested to use functions for modular programming
```
Void generate() / / generate Fibonacci sequence
{
}
Bool judge (int x) / / judge whether a number x is in the sequence
{
}
Int main() / / main function
{
return 0;
}
```
###Input format:
One line, positive integer n, (1 < n < = 1000000)
###Output format:
If n is not in the sequence, output - 1
###Input example:
Sample input 1:
```in
two
```
Sample input 2:
```in
eight
```
###Output example:
Sample output 1:
```out
three
```
Sample output 2:
```out
six
```







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