public class Fibonacci {

    public static void main (String[] argv)
    {
        // Test case 1:
        int n = 5;
        int f = fibonacci (n);
        System.out.println ("f(" + n + ") = " + f);

        // Test case 2:
        n = 20;
        f = fibonacci (n);
        System.out.println ("f(" + n + ") = " + f);
    }

    static int fibonacci (int n)
    {
        // Base cases:
        if (n == 1) {
            return 0;
        }
        else if (n == 2) {
            return 1;
        }
        
        // f_n = f_{n-1} + f_{n-2}
        int f_n_minus_one = fibonacci (n-1);
        int f_n_minus_two = fibonacci (n-2);

        return f_n_minus_one + f_n_minus_two;
    }

}