[Silver 3] 1406번 에디터

import java.util.*;
import java.io.*;

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        Stack<Character> left = new Stack<>();
        Stack<Character> right = new Stack<>();
        String str = br.readLine();
        
        for(int i=0; i<str.length(); i++) {
            left.push(str.charAt(i));
        }
        
        int n = Integer.parseInt(br.readLine());
        while(n-- > 0) {
            String s = br.readLine();
            if(s.charAt(0) == 'L' && !left.isEmpty()) {
                right.push(left.peek());
                left.pop();
            } else if(s.charAt(0) == 'D' && !right.isEmpty()) {
                left.push(right.peek());
                right.pop();
            } else if(s.charAt(0) == 'B' && !left.isEmpty()) {
                left.pop();
            } else if(s.charAt(0) == 'P') {
                left.push(s.charAt(2));
            }
        }
        
        while(!left.isEmpty()) {
            right.push(left.peek());
            left.pop();
        }
        
        while(!right.isEmpty()) {
            bw.write(right.peek());
            right.pop();
        }
        
        bw.flush();
    }
}