Return the n-th Fibonacci number. F(0) = 0, F(1) = 1, F(n) = F(n-1) + F(n-2).
Example 1
Input: n = 4
Output: 3
Explanation: Sequence: 0, 1, 1, 2, 3.
Output: 3
Explanation: Sequence: 0, 1, 1, 2, 3.
Example 2
Input: n = 2
Output: 1
Explanation: F(2) = F(1) + F(0) = 1 + 0 = 1.
Output: 1
Explanation: F(2) = F(1) + F(0) = 1 + 0 = 1.