HackerRank: Lonely Integer

https://www.hackerrank.com/challenges/lonely-integer
There are N integers in an array A. All but one integer occur in pairs. Your task is to find out the number that occurs only once.

https://codepair.hackerrank.com/paper/qz0v9rSh?b=eyJyb2xlIjoiY2FuZGlkYXRlIiwibmFtZSI6ImplZmZlcnl5dWFuIiwiZW1haWwiOiJ5dWFueXVuLmtlbm55QGdtYWlsLmNvbSJ9

    public static void main(String[] args) throws IOException {
    try {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int N = Integer.parseInt(br.readLine());
        boolean arr[] = new boolean[101];
        StringTokenizer st = new StringTokenizer(br.readLine());
        for (int i = 0; i < N; i++) {
            int a = Integer.parseInt(st.nextToken());
            arr[a] = !arr[a];
        }
        for (int i = 0; i < 101; i++) {
            if(arr[i]) {
                System.out.println(i);
                break;
            }
        }
        }
    catch(Exception e) {
    }