#include <iostream>
using namespace std;
int main()
{    
  double y=0,i=-1;
  int n=1, s;
  while(n<100)
    {
    	i=i*(-1);
    	n=n+1;
    	s=i*(1.0/n);
    	y=y+s;
	}
	cout<<y<<endl;
	return 0;
}