final int T = BigInteger.valueOf(14000000).nextProbablePrime().intValue();
    long[] was = new long[T];
    int[] sz = new int[T];

    void add(int p, int q) {
        long val = ((long) p << 32) ^ q;
        int pos = (int) (val % T);
        while (true) {
            if (was[pos] == 0 || was[pos] == val) {
                break;
            }
            pos++;
            if (pos == T) {
                pos = 0;
            }
        }
        was[pos] = val;
        sz[pos]++;
    }