static public int GetTriangleType(int? a, int? b, int? c)
        { 
            int Scalene = 1;
            int Isosceles = 2;
            int Equilateral = 3;
            int Error = 4;

            if ( (a != null) || (b != null) || (c != null) )
            {         
                if ( (a <= (b+c)) && (a >= (b-c)) )
                {
                    if ((b <= (a + c)) && (b >= (a - c)))
                    {
                        if ((c <= (a + b)) && (c >= (a - b)))
                        {
                            if ((a == b) && (b == c) && (c == a))
                                return Equilateral;
                            else if ((a == b) || (b == c) || (c == a))
                                return Isosceles;
                            else
                                return Scalene;
                        }
                    }
                }             
            }

            return Error;         
        }