46.求多项式（含浮点）

#include<stdio.h>
int main()
{
    int n,i; float sum;
    while(scanf("%d",&n)!=EOF){
        sum=0.0;
    for(i=1;i<=n;i++){
        if(i%2==0)
        sum=sum-(1.0/i);
        else
        sum=sum+(1.0/i);
    }
        printf("%.2f\n",sum);
    }
    return 0;
}