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 C# (judge verdict: Accepted)

using System;
using System.Collections.Generic;

namespace ConsoleApp1
{

    class Program
    {
        private static Dictionary<int, int> Dict = new System.Collections.Generic.Dictionary<int, int>();
        static void Main()
        {
            int n = int.Parse(Console.ReadLine());
            Console.WriteLine(fib(n));
        }
        private static int fib(int n) {
            if (n <= 1) return 1;
            if (Dict.ContainsKey(n)) return Dict[n];
            Dict[n] = fib(n - 1) + fib(n - 2);
            return Dict[n];
        }
    }
}