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int findJustSmaller(const vector<int>& arr, int target) {
    int low = 0;
    int high = arr.size() - 1;
    int result = -1;

    while (low <= high) {
        int mid = low + (high - low) / 2;

        // If the current element is smaller than or equal to the target,
        // we update the result and continue searching in the right half.
        if (arr[mid] <= target) {
            result = arr[mid];
            low = mid + 1;
        }
        // If the current element is greater than the target, we search in the left half.
        else {
            high = mid - 1;
        }
    }

    return result;
}