[실4] 10773 - 제로

#pragma region 라이브러리

#include <iostream>
#include <cmath>
#include <functional>
#include <vector>
#include <map>
#include <stack>
#include <queue>
#include <deque>

using namespace std;

#pragma endregion

#pragma region 최적화용

#define FAST_IO() ios::sync_with_stdio(0); cin.tie(0);
#define x first
#define x second

using IntPair = pair<int, int>;
using DoubleVec = vector<vector<int>>;
using Vec = vector<int>;

// 상하좌우
IntPair dir[]
{
	{ 1, 0 },
	{-1, 0 },
	{ 0, -1 },
	{ 0, 1 }
};

#pragma endregion

int main() 
{
	int t;
	cin >> t;
	stack<int> s;

	while (t--)
	{
		int n;
		cin >> n;

		if (n > 0)
			s.push(n);

		else
			s.pop();
	}
	int sum = 0;
	while (!s.empty())
	{
		sum += s.top(); 
		s.pop();
	}
	cout << sum;
	return 0;
}