// $Id: fibo.csharp,v 1.0 2002/02/14 10:49:00 dada Exp $
// http://dada.perl.it/shootout/

using System;

class App {

    public static int fib(int n) {
        return (n < 2) ? 1 : fib(n-2) + fib(n-1);
    }
    public static int Main(String[] args) {
        int N;
        int f;
        N = System.Convert.ToInt32(args[0]);
        if(N < 1) N = 1;
        f = fib(N);
        Console.WriteLine(f.ToString()+"\n");
        return(0);
    }
}