题解 | 数列求和

public class Main 
{
    public static void main(String[] args)
     {
        long i=9;
        long sum=0;
        int k=0;
        while(k<10)
        {
            sum+=i;
            i=i*10+9;
            k++;
        }
        System.out.print(sum);

    }
}