#include<stdio.h>
int main()
{
	int i = 0;
	double sum = 0.0;
	int flag = 1;
	for (i = 1;i <= 100;i++)
	{
		sum += 1.0 / i * flag;
		flag = -flag;
	}
	printf("sum=%lf\n", sum);
	return 0;
}