C :

#include<stdio.h>

int main()
{
	long n,i,t,c;
	double sum;
	while(scanf("%ld",&n),n!=0)
	{
		for(sum=0,c=0,i=1;i<=n-1;i++,c++)
			sum+=1.0/(n-c)*(c+1);
		sum=sum*2+n;
		printf("%.2lf\n",sum);
	}
	return 0;
}

C++ :

#include<stdio.h>

int main()
{
	long n,i,t,c;
	double sum;
	while(scanf("%ld",&n),n!=0)
	{
		for(sum=0,c=0,i=1;i<=n-1;i++,c++)
			sum+=1.0/(n-c)*(c+1);
		sum=sum*2+n;
		printf("%.2lf\n",sum);
	}
	return 0;
}

Pascal :

var n,i,j:longint;s:real;
begin
  readln(n);
  while n<>0 do
    begin
       s:=1*n;
       for i:=2 to n do
          s:=s+1/i*(n+1-i)*2;
      writeln(s:0:2);
      readln(n);
    end;
end.

Java :

import java.util.*;

public class Main{
    public static void main(String[] args){
    Scanner in = new Scanner(System.in);
    while(in.hasNextInt()){
        int N = in.nextInt();
        if(N==0) break;
        double sum = N;
        for(int up = 2*N-2, down = 2;down<=N;up-=2, down++)
            sum += up*1.0/down;
        System.out.printf("%.2f",sum);
        System.out.println("");
    }
}
}

Python :

while True:
    n = input()
    if n == 0:
        break
    s = n
    for i in range(2, n+1):
        s += (n-i+1)*(1.0/i)*2
    print "%.2f" % s