class Solution {
    public int solution(int[] A) {
        Arrays.sort(A);
        for (int i = 0; i < A.length; i = i + 2) {
            if (i + 1 == A.length)
                return A[i];
            if (A[i] != A[i + 1])
                return A[i];
        }
        return 0;
    }
}