class Solution {
    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
        if(root==null || root==p || root==q) return root;
        TreeNode L = lowestCommonAncestor(root.left,p,q);
        TreeNode R = lowestCommonAncestor(root.right,p,q);
        if(L!=null && R!=null) return root;
        if(L==null) return R;
        else return L;
    }
}