mport java.util.Scanner; //对级数一正两负的情况 public class test { public static void main(String[] args) {
Scanner reader=new Scanner(System.in);
System.out.print("请输入n:");
int n=reader.nextInt();
double sum=0.0;
int flag=0;
for(int i=1;i<=n;i++){
flag=i%3;
if(flag==1){
sum=sum+1.0/i;
} else{
sum=sum-1.0/i;
}
}
String result=String.format("%.2f",sum);
System.out.print("sum="+result);
}
}