public static Vector<Integer> solveVignereII(String cipherText) {
    Vector<Integer> ret = new Vector<Integer>();

    Map<String, Integer> tlas = new HashMap<String, Integer>();

    // find frequency of TLAs
    for (int i : new Range(cipherText.length() - 3)) {
        String tla = cipherText.substring(i, i + 3);
        if (tlas.containsKey(tla)) {
            tlas.put(tla, tlas.get(tla) + 1);
        } else {
            tlas.put(tla, 1);
        }
    }
    puts(tlas);

    Map<Integer, Integer> dists = new HashMap<Integer, Integer>();

    for (String k : tlas.keySet()) {
        if (tlas.get(k) < 2) {
            // tlas.remove(k);
        } else {
            int i = cipherText.indexOf(k);
            for (int n = cipherText.indexOf(k, i + 1);
                    n > 0;
                    i = n, n = cipherText.indexOf(k, n + 1)) {
                int dist = n - i;
                if (dists.containsKey(dist)) {
                    dists.put(dist, dists.get(dist) + 1);
                } else {
                    dists.put(dist, 1);
                }
            }
        }
    }
    puts(dists);

    for (int i : new Range(4, 21)) {
        int matchrate = 0;
        int total = 0;
        for (int d : dists.keySet()) {
            if (d % i == 0) {
                matchrate += dists.get(d);
            }
            total += dists.get(d);
        }
        puts("" + i + " " + matchrate + "/" + dists.size());
        if (matchrate > total * .9) {
            ret.add(i);
        }
    }
    puts(ret);

    return ret;
}