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/* The guess API is defined in the parent class GuessGame.
   @param num, your guess
   @return -1 if my number is lower, 1 if my number is higher, otherwise return 0
      int guess(int num); */

public class Solution extends GuessGame {
    public int guessNumber(int n) {
        int start = 1;
        int end = n;
        while(start <= end) {
            int mid = start + (end - start) / 2;
            if( guess(mid) == 0) {
                return mid;
            } else if(guess(mid) == -1) {
                end = mid - 1;
            } else {
                start = mid + 1;
            }
        }
        return end;
    }
}