（c++）1-2/3+3/5-4/7+5/9-6/11+...

输入格式:

Enter a positive integer n.

输出格式:

Output the value of the partial sum, retaining three decimal places.

 

#include
#include
using namespace std;
int main ()
{
    int n,i=1,x=1,y=1;
    float sum;
    cin>>n;
  while (i<=n)
  {
      sum+=i/(x*y*1.0);
      i++;
      x=-x;
      y=y+2;
  }
  cout< return 0;
}