278. First Bad Version 

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

        // now: [right, left]
        return left;
    }
}

References

278. First Bad Version