12번 암호문제 컴파일 에러가 나는 이유가 뭘까요?

package String;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class _01_12_암호_복습 {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int n = Integer.parseInt(br.readLine());
        String s = br.readLine().strip();
        s = s.replace('#', '1').replace('*', '0');
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < s.length(); i += 7) {
            String word = s.substring(i, i + 7);
            sb.append((char) Integer.parseInt(word, 2));
        }
        System.out.println(sb);
        br.close();
    }
}