计算2 + 22 + 222 + 2222 + ...

//12.计算2 + 22 + 222 + 2222 + ...

int n ,a , sum1 = 0, sum = 0;

    printf("请输入一个数a=");

    scanf("%d", &a);

    printf("请输入几位数n=");

    scanf("%d", &n);

    sum1 = a;

    sum = a;

        for (int i = 2; i <= n; i++) {

            sum  = sum + a * 10;

            a = a * 10;

            sum1  = sum1 + sum;

        }

        printf("和是:%d",sum1);