int maxDepth(TNODE *root){
    if (!root) return 0;
    if (root && !root.m_L && !root.m_R) return 1;
    int counterL = maxDepth(root.m_L);
    int counterR = maxDepth(root.m_R);
    if (counterL > counterR) return 1 + counterL;
    else return 1 + counterR;
}