第九周项目二：分数的累加

#include <iostream>

using namespace std;

int main()
{
    int s=1;
    double n=1,sum=0,total;
    while(n<=19)
    {
       total=n/(n+2);
       sum=sum+s*total;
       s=-s;
       n=n+2;
    }

    cout<<"1/3-3/5+5/7-...+19/21的结果为："<<sum<<endl;
    return 0;
}