#include <iostream>
using namespace std;
int main()
{int i;
 long double j,n=1;
 for(i=2;i<=100;i++)
   {if(i%2==0) j=-1.0/i;
    else j=1.0/i;
    n=n+j;
   }
cout<<"n="<<n<<endl;
system ("pause");
return 0;
}