python3

javascript

java

Fibonacci Number

The Fibonacci numbers, commonly denoted F(n) form a sequence, called the Fibonacci sequence, such that each number is the sum of the two preceding ones, starting from 0 and 1. That is,

```
F(0) = 0, F(1) = 1
F(n) = F(n - 1) + F(n - 2), for n > 1.  
```
Given n, calculate F(n).

**Try doing it in both recursive and iterative method**     
### Input Format

First Parameter - Integer `n`

### Output Format

Return the integer

### Example 1:
```txt
Input:
    3
Output:
    2
Explanation:
    F(3) = F(2) + F(1) = 1 + 1 = 2.
```

### Example 2:
```txt
Input:
    4
Output:
    3
Explanation:
    F(4) = F(3) + F(2) = 2 + 1 = 3.
```
#### Constraints:
- 0 <= n <= 30
