[BOJ] 10773 제로

#include <iostream>
#include <stack>

int main() {
    int command_count, sum = 0;
    std::stack<int> pc;
    
    std::cin >> command_count;

    for (int i = 0; i < command_count; i++) {
        int a;
        std::cin >> a;
        if (a == 0 && !pc.empty()) {
            pc.pop();
        } else {
            pc.push(a);
        }
    }

    while (!pc.empty()) {
        sum += pc.top();
        pc.pop();
    }

    std::cout << sum << std::endl;
    return 0;
}