/*  Create a function that takes an array of numbers and return the number
 *  that's unique.
 */
  // a a a a b -> abaaa returns '2'
  // c d d d d d -> cddddd returns '2'
double unique(std::vector<double> arr) {
	std::sort (arr.begin(),arr.end());
	std::unique (arr.begin(),arr.end());
	//  expression ? trueValue : falseValue
	return arr[1]!=arr[2] ? arr[1] : arr[0];
}