1 #include "bits/stdc++.h"
2 using namespace std;
3 const int MAX=1e5+5;
4 int n,cnt,d[MAX],num[MAX],nu;
5 vector <int> adj[MAX];
6 double f[MAX],ans;
7 int main(){
8 freopen ("f.in","r",stdin);
9 freopen ("f.out","w",stdout);
10 int i,j,u,v,zt,now;
11 vector <int> x;
12 scanf("%d",&n);
13 for (i=1;i<n;i++){
14 scanf("%d%d",&u,&v);
15 adj[u].push_back(v);
16 adj[v].push_back(u);
17 }
18 queue <int> q;
19 while (!q.empty()) q.pop();
20 q.push(1);now=1;
21 memset(f,0,sizeof(f));
22 f[1]=1;
23 while (!q.empty()){
24 zt=q.front();q.pop();
25 for (i=1;i<=adj[zt].size();i++)
26 f[now+i]=1.0/(double)(now+i)+(double)(f[now+i-1]+1)*(double)(i)/(double)(now+i);
27 now+=adj[zt].size();
28 }
29 memset(d,0,sizeof(d));
30 d[1]=1;q.push(1);
31 memset(num,0,sizeof(num));
32 nu=0;
33 while (!q.empty()){
34 zt=q.front();q.pop();
35 nu=max(nu,d[zt]);
36 num[d[zt]]++;
37 //cout<<zt<<' '<<d[zt]<<' '<<num[d[zt]]<<endl;
38 for (i=0;i<adj[zt].size();i++){
39 if (d[adj[zt][i]]!=0) continue;
40 d[adj[zt][i]]=d[zt]+1;
41 q.push(adj[zt][i]);
42 //cout<<"fuck "<<zt<<' '<<adj[zt][i]<<endl;
43 }
44 }
45 //cout<<nu<<endl;
46 for (i=1;i<=nu;i++){
47 //cout<<num[i]<<' ';
48 ans+=(double)num[i]/(double)i;
49 }//cout<<endl;
50 printf("%.8lf",ans);
51 return 0;
52
