hdu 2156 分数矩阵

import java.util.Scanner;
public class Main{
public static void main(String[] args) {
Scanner input=new Scanner(System.in);
while(true){
int n=input.nextInt();
if(n==0)
break;
double sum=0;
for(int i=2;i<=n;i++){
sum+=(n-i+1)*(1.0/i);
}
sum=sum*2+n;
System.out.printf("%.2f",sum);
System.out.println();
}
}
}