1-1/2+1/3-1/4.........

#include<stdio.h>
int main(void)
{
    int i,n,f,d,m;
    double sum,item;
    f=1;
    d=1;
    sum=0;
    scanf("%d",&n);   
    for(i=1;i<=m;i++){
        scanf("%d",&m);
        item=f*1.0/d;
        sum=sum+item;
        f=-f;
        d=d+1;
    printf("%.2f\n",sum);
    }
    return 0;

}