double n = 1;
        double h = (b - a) / n;

        double ih = 1;
        double previous = 0;

        while (Math.Abs(ih - previous) >= 3 * epsilon) {

            previous = ih;

            double sum = 0;
            for (int i = 1; i < n; ++i) {
                sum += 2 * Function1(i * h + a);
            }

            ih = (sum + Function1(a) + Function1(b)) * h / 2;

            n *= 2;
            h /= 2;
        }

        return ih;