多项式求和

#include<stdio.h>
main()
{
    int m,n,i,j,a;
    double sum;
    while(scanf("%d",&m)!=EOF)
    {
        while(m--)
        {
            scanf("%d",&a);
            sum=0;
            for(j=1;j<=a;j++)
            {
                if(j%2==0)
                    sum+=-1.0/j;
                else
                    sum+=1.0/j;
            }
            printf("%.2lf\n",sum);
        }
    }
}