public static int binSearchIter(Integer[] a, int x) {
        int l=-1, r=a.length, m=0;
        //inv: a[l]>x && a[r]<=x
        while (l < r - 1) {
            m = l + (r - l) / 2;
            if (a[m] > x) {
                l = m;
            } else {
                r = m;
            }
        }
        if (r >= a.length || a[r] != x) {
            return -r - 1;
        }
        return r;
    }