题解 | #[NOIP2015]金币#

int main()
{
	int a, b, c;
	int sum = 0;
	int d = 0;

	scanf("%d", &a);

	for (b = 1; d < a; b++)
	{
		for (c = 0; c < b; c++)
		{
			sum += b;
			d++;
			if (d == a)
			{
				break;
			}
		}
	}

	printf("%d\n", sum);
	return 0;
}