分数加减

int main()
{
	int a = 0;
	double sum = 0.0;
	for (a = 1; a <= 100; a++)
	{
		sum += 1.0 / a;
	}
	printf("%lf\n", sum);
	return 0;
}

int main()
{
	int a = 0;
	double sum = 0.0;
	int b = 1;
	for (a = 1; a <= 100; a++)
	{
		sum += b * 1.0 / a;
			b = -b;
	}
	printf("%lf\n", sum);
	return 0;
}