/**
 * 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) {}
 * };
 */
typedef long long LL;
const int mod = 1e9 + 7;
class Solution {
public:
    LL sum, ans = 0;

    LL getSum(TreeNode* node){
        if (!node)  return 0;
        return getSum(node->left) + getSum(node->right) + node->val;
    }

    LL dfs(TreeNode* node){
        if (!node)  return 0;
        LL sum_d = dfs(node->left) + dfs(node->right) + node->val;
        ans = max(ans, sum_d * (sum - sum_d));
        return sum_d;
    }

    int maxProduct(TreeNode* root) {
        sum = getSum(root);
        dfs(root);
        return ans % mod;
    }
};