## 1. Problem

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).

Example 1:

```
Input: n = 2
Output: 1
Explanation: F(2) = F(1) + F(0) = 1 + 0 = 1.
```

Example 2:

```
Input: n = 3
Output: 2
Explanation: F(3) = F(2) + F(1) = 1 + 1 = 2.
```

Example 3:

```
Input: n = 4
Output: 3
Explanation: F(4) = F(3) + F(2) = 2 + 1 = 3.
```

Constraints:

- 0 <= n <= 30

## 2. Solution

I solved this problem like this.

- Complexity
- Time complexity : O(N)
- Space complexity : O(N)

- Step
- Using for statement, add new values.

```
class Solution:
def fib(self, n: int) -> int:
li = [0, 1]
for i in range(30):
li.append(sum(li[-2:]))
return li[n]
```