MODULE Main;
IMPORT Fmt, Scan, Params, Wr, Stdio;

PROCEDURE fib(n: INTEGER): INTEGER =
BEGIN
    IF n < 2 THEN
        RETURN 1;
    ELSE
        RETURN fib(n-2) + fib(n-1);
    END
END fib;

VAR N: INTEGER;
BEGIN
    IF Params.Count > 0 THEN
        N := Scan.Int(Params.Get(1));
    ELSE
        N := 1;
    END;
    Wr.PutText (Stdio.stdout, Fmt.Int(fib(N)));
    Wr.Close (Stdio.stdout);
END Main.