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