MODULE Sudan;
FROM InOut IMPORT WriteCard, WriteString, WriteLn;

PROCEDURE sudan(n, x, y: CARDINAL): CARDINAL;
    VAR k: CARDINAL;
BEGIN
    IF n = 0 THEN RETURN x+y
    ELSIF y = 0 THEN RETURN x
    ELSE
        k := sudan(n, x, y-1);
        RETURN sudan(n-1, k, k+y)
    END
END sudan;

PROCEDURE Show(n, x, y: CARDINAL);
BEGIN
    WriteString("sudan(");
    WriteCard(n, 0);
    WriteString(", ");
    WriteCard(x, 0);
    WriteString(", ");
    WriteCard(y, 0);
    WriteString(") = ");
    WriteCard(sudan(n,x,y), 0);
    WriteLn
END Show;

BEGIN
    Show(0, 0, 0);
    Show(1, 1, 1);
    Show(2, 1, 1);
    Show(3, 1, 1);
    Show(2, 2, 1)
END Sudan.