c#include <bits/stdc++.h> using namespace std; int main(){ cin.tie(NULL); cout.tie(NULL); ios_base::sync_with_stdio(false); int K; cin >> K; int sum = 0; stack<int> numbers; for(int i = 0; i < K; i++){ int num; cin >> num; if(num == 0){ sum -= numbers.top(); numbers.pop(); }else{ sum += num; numbers.push(num); } } cout << sum; return 0; }```