找规律

#include<stdio.h>
int main(){
int n;
scanf("%d",&n);
double sum = 0;
//根据给定算式能看出分母是1，-2,3，-4，...，n
//即分母为偶数时为负数
for(int i = 1;i <= n;i++){
if(i%2 != 0){
sum += 1.0/i;
}else{
sum += (1.0/i)*(-1);
}
}
printf("%.3lf",sum);
return 0;
}