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/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    string ans;
    void rootToStart(TreeNode* root, int startValue,int cnt) {
        if(root == NULL)return;
        if(root->val == startValue) {
            for(int i=0;i<cnt;i++) {
                ans.push_back('U');
            }
            return;
        }
        
        rootToStart( root->left, startValue, cnt+1);
        rootToStart( root->right, startValue, cnt+1);
        
    }
    
    bool rootToDest(TreeNode* root, int destValue) {
        if(root == NULL)return false;
        if(root->val == destValue) {
            return true;
        }

        ans.push_back('L');
        if(rootToDest(root->left, destValue)) return true;
        
        ans.pop_back();
        
        ans.push_back('R');
        if(rootToDest(root->right, destValue)) return true;
        ans.pop_back();
        
        return false;
        
    }
    
    TreeNode* findLCA(TreeNode* root, int startValue, int destValue) {
        if(root == NULL)return NULL;
        
        if(root->val == startValue || root->val == destValue) return root;
        
        TreeNode* leftLCA = findLCA(root->left, startValue, destValue);
        TreeNode* rightLCA = findLCA(root->right, startValue, destValue);
        
        if(leftLCA == NULL) return rightLCA;
        if(rightLCA == NULL) return leftLCA;
        
        return root;      
    }
    
    string getDirections(TreeNode* root, int startValue, int destValue) {    
        TreeNode* lca = findLCA(root, startValue, destValue);
        rootToStart(lca, startValue, 0);
        rootToDest(lca, destValue);
        return ans;
    }
};