[백준]10773-제로(설명X)

#include <cstdio>
#include <stack>
using namespace std;
 
int main()
{
    stack<int> stk;
    int K;
    scanf("%d", &K);
    for (size_t i = 0; i < K; i++) {
        int num;
        scanf("%d", &num);
        if (num == 0)
            stk.pop();
        else
            stk.push(num);
    }
    int sum = 0;
    int size = stk.size();
    for (size_t i = 0; i < size; i++) {
        sum += stk.top();
        stk.pop();
    }
    printf("%d", sum);
    return 0;
}