1public class Solution extends GuessGame {
2    public int guessNumber(int n) {
3        int left = 1, right = n;
4        
5        while (left <= right) {
6            int mid = left + (right - left) / 2;
7            int result = guess(mid);
8            
9            if (result == 0) {
10                return mid;
11            } else if (result < 0) {
12                right = mid - 1;
13            } else {
14                left = mid + 1;
15            }
16        }
17        
18        return -1;
19    }
20}