class Solution {
static int height=-1;
    public int solution(Tree T) {
        if (T == null) return height;
        height = heightOfTree(T);
        return height;
    }

    public int heightOfTree(Tree node) {
        if (node != null) {
            if (node.l == null) {
                return heightOfTree(node.r);
            }
            if (node.r == null) {
                return 1 + heightOfTree(node.l);
            } else {
                return 1 + Math.max(heightOfTree(node.r), heightOfTree(node.l));
            }
        }
        return 0;
    }

}