Solution.java

class BinaryIndexedTree {
    private int n;
    private int[] c;

    public BinaryIndexedTree(int n) {
        this.n = n;
        this.c = new int[n + 1];
    }

    public void update(int x, int delta) {
        for (; x <= n; x += x & -x) {
            c[x] += delta;
        }
    }

    public int query(int x) {
        int s = 0;
        for (; x > 0; x -= x & -x) {
            s += c[x];
        }
        return s;
    }
}

class StreamRank {
    private BinaryIndexedTree tree = new BinaryIndexedTree(50010);

    public StreamRank() {
    }

    public void track(int x) {
        tree.update(x + 1, 1);
    }

    public int getRankOfNumber(int x) {
        return tree.query(x + 1);
    }
}

/**
 * Your StreamRank object will be instantiated and called as such:
 * StreamRank obj = new StreamRank();
 * obj.track(x);
 * int param_2 = obj.getRankOfNumber(x);
 */