public static int nonDivisibleSubset(int k, List<Integer> s) {
    Map<Integer, Integer> modToCount = new HashMap<>();
    for (Integer q : s) {
        int r = q % k;
        int c = modToCount.getOrDefault(r, 0); 
        c++;
        modToCount.put(r, c); 
    }
    if (modToCount.containsKey(0)) {
        modToCount.put(0, 1); 
    }   
    if (k % 2 == 0 && modToCount.containsKey(k / 2)) {
        modToCount.put(k / 2, 1); 
    }   
    Set<Integer> skip = new HashSet<>();
    int count = 0;
    for (Integer rem : modToCount.keySet()) {
        if (skip.contains(rem)) {
            continue;
        }   
        int bad = k - rem;
        int val = modToCount.get(rem);
        if (modToCount.containsKey(bad)) {
            if (modToCount.get(bad) > val) {
                val = modToCount.get(bad);
            }   
            skip.add(bad);
        }   
        count += val;
    }   
    return count;
}