long a = (long)num;
        if (a == num)
            return Long.toString(a);
        else {
            long n = Double.toString(num).length() - Long.toString(a).length() - 1;
            if (n < 14) num = Math.round(num * Math.pow(10, n))/Math.pow(10, n);
            else num = Math.round(num * Math.pow(10, 14))/Math.pow(10, 14);

            a = (long)num;  // tranh TH sau khi bien doi lai ve so nguyen VD (Tan(pi/4))
            if (a == num)
                return Long.toString(a);
            else return Double.toString(num);
        }