问C语言如何计算 a+aa+aaa+…+aa…a（n个a）的值？

long E(int m)
{
	long num = 1;
	while (m) {
		num *= 10;
		m--;
	}
	return num;
}

long GenNum(int num, int count)
{
	long ret = 0;
	while (count) {
		count--;
		ret += num * E(count);
	}
	return ret;
}

int main() {
	int a, n;
	printf("Input a,n:\n");
	scanf("%d,%d", &a, &n);
	long sum = 0;
	while (n) {
		sum += GenNum(a, n);
		n--;
	}
	printf("sum=%ld\n", sum);
	return 0;
}