2020 号门牌，总共需要多少个字符 2

public static void main(String[] args) {
     number3(2020,2);
}        

public static int number3(int a, int b){
    int ans = 0;
    for (int i = 1; i <= a; i++){
        String s = String.valueOf(i);
        for (int j=0; j