Given a balanced binary tree find sum of all the nodes .... what is wrong in this code

#1

#include<bits/stdc++.h>
#define ll long long int
using namespace std;

class node{
public:
int data;
nodeleft;
noderight;

    node(int d){
        data = d;
        left = NULL;
        right = NULL;
    }

};

node* buildTree(){
int d;
cin>>d;
node * root = new node(d);
root->left = buildTree();
root->right = buildTree();
return root;
}

int sumBT(node*root){
if(root==NULL){
return 0;
}
return (root->data+sumBT(root->left)+sumBT(root->right));
}

int main(){
ll n;cin>>n;
node* root;
ll sum=0;
for(ll i=0;i<n;i++){
root=buildTree();
sum=sumBT(root);
}

cout<<sum<<endl;

return 0;

}