MODULE ArithmeticDerivative; (* Translation of Algol W *)
    IMPORT Out;
    VAR    n              : INTEGER;

    PROCEDURE lagarias( n : INTEGER ) : INTEGER; (* Lagarias arithmetic derivative *)
        VAR   result, f, q            : INTEGER;

        PROCEDURE smallPf( j, k : INTEGER ) : INTEGER; (* Smallest prime factor *)
            VAR   result        : INTEGER;
            BEGIN
                IF j MOD k = 0 THEN result := k
                ELSIF k = 2    THEN result := smallPf( j, 3 )
                ELSE                result := smallPf( j, k + 2 )
                END
            RETURN result
            END smallPf ;

        BEGIN
            IF n < 0 THEN result := - lagarias( - n )
            ELSIF ( n = 0 ) OR ( n = 1 ) THEN result := 0
            ELSE
                f := smallPf( n, 2 ); q := n DIV f;
                IF q = 1 THEN result := 1 ELSE result := q * lagarias( f ) + f * lagarias( q ) END
            END
        RETURN result
        END lagarias ;

BEGIN
    FOR n := -99 TO 100 DO
       Out.String( " " );Out.Int( lagarias( n ), 6 );
       IF n MOD 10 = 0 THEN Out.Ln END
    END
END ArithmeticDerivative.