avoidObstacles.cs

  int avoidObstacles(int[] inputArray)
        {
            var jump = 2;
            var max = inputArray.Max() + 1;
            while (jump <= max)
            {
                int multiplier = 1;
                bool success = false;
                while (true)
                {
                    var number = jump * multiplier;
                    if (number > max) break;
                    if (Array.IndexOf(inputArray, number) != -1)
                    {
                        success = false;
                        break;
                    }
                    multiplier++;
                    success = true;
                }
                if (success) break;
                jump++;
            }

            return jump;
        }