awk -F "" ' BEGIN{ ORS=""; OFS="";

} { if(NF <= 3){print 0;} else { a=NF%3;

        for(i=0;i<=NF;i++)
        {
            if(i == a&&a < NF)
            {
                if(i!=0)printf ",";
                a+=3;
            
            }
            print $(i+1);
            
        }
    
    }
printf "\n";

}' #a=' *';

#for i in seq 5 ; #do #echo "a";a=a";a=a' *';a=${a:1};

#done;

#sed -rn 's/([0-9]{3})>/,\1/p' nowcoder.txt