/* The isBadVersion API is defined in the parent class VersionControl.
      boolean isBadVersion(int version); */

public class Solution extends VersionControl {
    public int firstBadVersion(int n) {
        int left = 1;
        long right = n;
        
        while (left <= right) {
            int mid = (int)((left + right) >> 1);
            if (isBadVersion(mid)) {
                right = mid - 1;
            } else {
                left = mid + 1;
            }
        }
        
        return left;
    }
}