AC

#include <bits/stdc++.h>
using namespace std;

struct TreeNode {
	int val;
	TreeNode *left;
	TreeNode *right;
	TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
};


TreeNode *buildTree(const vector<int> &arr, int &id) {
	if (id >= arr.size() || arr[id] == -1) {
		id++;
		return nullptr;
	}
	TreeNode *root = new TreeNode(arr[id]);

	id++;
	root->left = buildTree(arr, id);
	root->right = buildTree(arr, id);
	return root;
}


void dfs(TreeNode *root, int &sum, const vector<int> &arr, bool isLeft) {
	if (!root)
		return;


	if (!root->left && !root->right && isLeft) {
		sum += root->val;
		return;
	}


	dfs(root->left, sum, arr, 1);

	dfs(root->right, sum, arr, 0);
}

int main() {
	vector<int> arr;
	int t;

	while (cin >> t) {
		arr.push_back(t);
		if (cin.get() == '\n')
			break;
	}

	int id = 0;
	TreeNode *root = buildTree(arr, id);
	int sum = 0;
	dfs(root, sum, arr, 0);
	cout << sum << endl;
	return 0;
}