UVA - 11063 - B2-Sequence

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.HashSet;
import java.util.StringTokenizer;

public class Main {

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringBuilder sb = new StringBuilder();
        String m;
        int cases = 1;
        while ((m = br.readLine()) != null) {
            int[] arr = new int[Integer.parseInt(m)];
            StringTokenizer st = new StringTokenizer(br.readLine());
            HashSet<Integer> hs = new HashSet<Integer>();
            for (int i = 0; i < arr.length; i++) {
                arr[i] = Integer.parseInt(st.nextToken());
            }
            boolean flag = false;
            if (arr[0] < 1) {
                flag = true;
            }
            if (flag) {
                sb.append("Case #").append(cases).append(": It is not a B2-Sequence.\n\n");
                cases++;
                br.readLine();
                continue;
            }
            for (int i = 0; i < arr.length - 1; i++) {
                if (arr[i] >= arr[i + 1]) {
                    flag = true;
                    break;
                }
            }
            if (flag) {
                sb.append("Case #").append(cases).append(": It is not a B2-Sequence.\n\n");
                cases++;
                br.readLine();
                continue;
            }
           
            for (int i = 0; i < arr.length; i++) {
                for (int j = i ; j < arr.length; j++) {
                    int temp = arr[i] + arr[j];
                    if (hs.contains(temp)) {
                        flag = true;
                        break;
                    }
                    hs.add(temp);
                }
                if (flag) {
                    break;
                }
            }
            if (flag) {
                sb.append("Case #").append(cases).append(": It is not a B2-Sequence.\n\n");
                cases++;
            } else {
                sb.append("Case #").append(cases).append(": It is a B2-Sequence.\n\n");
                cases++;
            }
            br.readLine();
        }
        System.out.print(sb);
    }
}