[백준][Java] 10773번 제로

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Stack;
 
 
public class Main {
        
    private static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
//    private static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
    
    
    
    public static void main(String[] args) throws IOException{
        int N = Integer.parseInt(br.readLine());
        int res = 0;
        Stack<String> st = new Stack<>();
        
        for(int i=0; i<N; i++) {
            String input = br.readLine();
            if(input.equals("0")) st.pop();
            else st.push(input);
        }
        
        while(!st.isEmpty()){
            res+=Integer.parseInt(st.pop());
        }
        
        System.out.println(res);
        
        
    }
}