/**
 * struct TreeNode {
 *	int val;
 *	struct TreeNode *left;
 *	struct TreeNode *right;
 * };
 */

class Solution {
public:
    /**
     * 
     * @param root TreeNode类 
     * @param o1 int整型 
     * @param o2 int整型 
     * @return int整型
     */
    TreeNode* find(TreeNode* T,int x1,int x2){
        if(T==nullptr||T->val==x1||T->val==x2){
            return T;
        }
        TreeNode* l= find(T->left,x1,x2);
        TreeNode* r=find(T->right,x1,x2);
        if(r==nullptr) return l;
        if(l==nullptr) return r;
        return T;
    }
    int lowestCommonAncestor(TreeNode* root, int o1, int o2) {
        // write code here
        return find(root,o1,o2)->val;
    }
};