RT。求助大佬这个代码ans期望输出多少？最坏输出多少？（用带 $n$ 的关系式回答）

signed main()
{
	srand((unsigned long long)new char);
	scanf("%lld",&n);
	for(int i = 1;i <= n;i++)
	{
		a[i] = rand() % n + 1,b[i] = rand() % n + 1;
		printf("%lld %lld\n",a[i],b[i]);
		int res = 0x3f3f3f3f;
		for(int j = 1;j < i;j++)
		{
			if(abs(a[j] - a[i]) + abs(b[j] - b[i]) < res)
				res = abs(a[j] - a[i]) + abs(b[j] - b[i]);
		}
		if(i != 1)
			ans += res;
	}
	printf("ans = %lld\n",ans);
}

代码翻译：每次加一个点，并求出与这个点曼哈顿距离最小的点的距离，加进ans