package A;
public class Main {
    public int singleNumber(int[] numbers) {
        int s = 0;
        for (int i = 0; i < numbers.length; i++) {
            s = s ^ numbers[i];
        }
        return s;
    }

    public static void main(String[] args) throws Exception {
        int[] numbers = {1, 1, 2, 2, 3, 3, 4, 5, 5, 6, 6};
        System.out.println(new Main().singleNumber(numbers));
    }


}