/* 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, right = n, middle;

        while (left < right) {
            middle = left + (right - left) / 2;

            if (isBadVersion(middle)) {
                right = middle;
            } else {
                left = middle + 1;
            }
        }

        return left;
    }
}

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