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: Time Limit Exceeded)

using System;

namespace A
{
    class Calc
    {
        public int fib(int n)
        {
            if (n==1 || n==0)
            {
                return 1;
            }
            else
            {
                return fib(n-1)+fib(n-2);
            }
        }
    }

    class A
    {
        static void Main(string[] args)
        {
            string input = Console.ReadLine();
            int n = int.Parse(input);
            Calc calc = new Calc();
            Console.WriteLine(calc.fib(n));
        }
    }
}