4번 문제 runtime error

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        List<String> strList = new ArrayList<>();
        List<StringBuilder> flipWords = new ArrayList();
        int input1 = 0;

        while (true) {
            Scanner in=new Scanner(System.in);

            if (input1 == 0) {
                input1 = in.nextInt();
            } else {
                if (strList.size() != input1) {
                    strList.add(in.nextLine());
                } else {
                    break;
                }
            }
        }

        for(int i=0; i<strList.size(); i++) {
            String str = strList.get(i);
            StringBuilder sb = new StringBuilder();
            for(int j=str.length() - 1; j>=0; j--){
                sb.append(str.charAt(j));
            }
            flipWords.add(sb);
        }

        for(int i=0; i<flipWords.size(); i++){
            System.out.println(flipWords.get(i));
        }
    }

}