/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 * @param {TreeNode} p
 * @param {TreeNode} q
 * @return {TreeNode}
 */
var lowestCommonAncestor = function(root, p, q) {
    if(root === null || root === p || root === q){
        return root;
    }   
    let l = lowestCommonAncestor(root.left, p, q);
    let r = lowestCommonAncestor(root.right, p, q);
    if(!l) return r;
    if(!r) return l;

    return root;
};