Java，大佬帮我康康，为啥只有20分

package P1320压缩技术续集版;

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner reader=new Scanner(System.in);
        String s1= reader.nextLine();//读取第一行
        int n=s1.length();//获得一共几行
        for(int i=1;i<n;i++){
            s1+= reader.nextLine();
        }
        System.out.print(n+" ");//打印方阵行数
        int count=0;
        int num=1;
        while (num<=n*n){
            count++;
            if(num==n*n){
                System.out.println(count);
            }else{
                if(s1.charAt(num-1)!=s1.charAt(num)){
                    System.out.print(count+" ");
                    count=0;
                }
            }
            num++;
        }

    }
}