private int bsearch(int[] a, int x) {
        int low = 0;
        int high = a.length - 1;
        int mid;

        if (a[0] < x) {
            return 0;
        }

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

            if (a[mid] > x)
                low = mid + 1;
            else if (a[mid] < x)
                high = mid - 1;
            else
                return mid + 1;
        }

        return -1;
    }