题解 | 数列求和

public class Main {
    public static void main(String[] args) {

        //write your code here........
        long sum = 0;
        long term = 0;

        int i = 0;
        for(i = 0; i < 10; i++){
            term = term * 10 + 9;
            sum += term;
        }

        System.out.println(sum);
    }
}