Problem:
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Fibonacci Number

Write a program which prints $n$-th fibonacci number for a given integer $n$. The $n$-th fibonacci number is defined by the following recursive formula:

\begin{equation*}
fib(n)= \left \{
\begin{array}{ll}
1　 & (n = 0) \\
1　 & (n = 1) \\
fib(n - 1) + fib(n - 2) & \\
\end{array}
\right.
\end{equation*}

Input

An integer $n$ is given.

output

Print the $n$-th fibonacci number in a line.

Constraints

$0 \leq n \leq 44$

Sample Input 1

3

Sample Output 1

3

Solution in Python3 (judge verdict: Accepted)

n = int(input())
memo = [-1]*(n+1)
memo[0] = 1
memo[1] = 1

def fib(n):
    if memo[n] != -1:
        return memo[n]
    else:
        ans = fib(n-1)+fib(n-2)
        memo[n] = ans
        return ans

print(fib(n))