1 #include<bits/stdc++.h>
  2 using namespace std;
  3 const int maxn=2E3+5;
  4 int n;
  5 int deg[maxn*2],hh[maxn];
  6 int tot,haha;
  7 bool dot[maxn];
  8 vector<int>what[maxn];
  9 vector<int>wait;
 10 double w[maxn];
 11 map<pair<int,int>,bool>vis;
 12 inline pair<int,int>M(int x,int y)
 13 {
 14     if(x>y)
 15         swap(x,y);
 16     return make_pair(x,y); 
 17 }
 18 struct edge
 19 {
 20     int to,next;
 21     double w;
 22 };
 23 struct note
 24 {
 25     int x,y;
 26     double d;
 27     note(int a=0,int b=0,double c=0)
 28     {
 29         x=a,y=b,d=c;
 30     }
 31 };
 32 vector<note>ans;
 33 struct graph
 34 {
 35     int head[maxn*2],size;
 36     edge E[maxn*2]; 
 37     inline void add(int u,int v,double w)
 38     {
 39         E[++size].to=v;
 40         E[size].next=head[u];
 41         E[size].w=w;
 42         head[u]=size;
 43     }
 44     void get(int u,int F,int num)
 45     {
 46         for(int i=head[u];i;i=E[i].next)
 47         {
 48             int v=E[i].to;
 49             if(v==F)
 50                 continue;
 51             if(u==F)
 52             {
 53                 w[++num]=E[i].w;
 54                 hh[num]=v;
 55                 get(v,u,num);
 56             }
 57             else
 58                 get(v,u,num);
 59         }
 60         if(deg[u]==1)
 61             what[num].push_back(u); 
 62         if(u==F)
 63             for(int i=1;i<=num;++i)
 64             {
 65                 if(vis[M(u,hh[i])])
 66                     continue;
 67                 if(what[i].size()==1)
 68                 {
 69                     int u1=what[i][0];
 70                     int x=what[i+1<=num?i+1:i+1-num][0];
 71                     int y=what[i+2<=num?i+2:i+2-num][0];
 72                     double d=w[i]/2;
 73                     ans.push_back(note(u1,x,d));
 74                     ans.push_back(note(u1,y,d));
 75                     ans.push_back(note(x,y,-d));
 76                     vis[M(u,hh[i])]=1;
 77                 }
 78                 else
 79                 {
 80                     int u1=what[i][0],u2=what[i][what[i].size()-1];
 81                     int x=what[i+1<=num?i+1:i+1-num][0];
 82                     int y=what[i+2<=num?i+2:i+2-num][0];
 83                     double d=w[i]/2;
 84                     ans.push_back(note(u1,x,d));
 85                     ans.push_back(note(u2,y,d));
 86                     ans.push_back(note(u1,u2,-d));
 87                     ans.push_back(note(x,y,-d));
 88                     vis[M(u,hh[i])]=1;
 89                 }
 90             }
 91     }
 92     void find(int u,int F,int last)
 93     {
 94         dot[u]=1;
 95         if(deg[u]!=2)
 96         {
 97             haha=last;
 98             wait.push_back(u);
 99             return;
100         }
101         for(int i=head[u];i;i=E[i].next)
102         {
103             int v=E[i].to;
104             if(v==F)
105                 continue;
106             if(last==1)
107             {
108                 find(v,u,E[i].w);
109                 last=E[i].w;
110             }
111             else if(last==E[i].w)
112                 find(v,u,E[i].w);
113             else
114             {
115                 cout<<"NO"<<endl;
116                 exit(0);
117             }
118         }
119     }
120     int sum;
121     void getsize(int u,int F)
122     {
123         ++sum;
124         for(int i=head[u];i;i=E[i].next)
125         {
126             int v=E[i].to;
127             if(v==F)
128                 continue;
129             getsize(v,u);
130         }
131     }
132 }source,G;
133 int main()
134 {
135     ios::sync_with_stdio(false);
136     cin>>n;
137     for(int i=2;i<=n;++i)
138     {
139         int x,y;
140         double z;
141         cin>>x>>y>>z;
142         source.add(x,y,z);
143         source.add(y,x,z);
144         ++deg[x],++deg[y];
145     }
146     int P1=1,P2=2;
147     for(int u=1;u<=n;++u)
148     {
149         if(deg[u]==2)
150         {
151             if(!dot[u])
152             {
153                 source.find(u,u,1);
154                 wait.clear();
155                 G.add(wait[0],wait[1],haha);
156                 G.add(wait[1],wait[0],haha);
157                 P1=wait[0],P2=wait[1];
158             }
159             continue;
160         }
161         for(int i=source.head[u];i;i=source.E[i].next)
162         {
163             int v=source.E[i].to;
164             haha=source.E[i].w;
165             if(deg[v]!=2)
166                 G.add(u,v,source.E[i].w);
167         }
168     }
169     cout<<"YES"<<endl;
170     G.getsize(P1,P1);
171     if(G.sum==2)
172     {
173         cout<<1<<endl;
174         cout<<P1<<" "<<P2<<" "<<haha<<endl;
175         return 0;
176     }
177     for(int u=1;u<=n;++u)
178     {
179         if(deg[u]==1)
180             continue;
181         for(int i=1;i<=n;++i)
182             what[i].clear();
183         G.get(u,u,0);
184     }
185     int del=0;
186     for(int i=0;i<ans.size();++i)
187         if(abs(ans[i].d-0)<=0.01)
188             ++del;
189     cout<<ans.size()-del<<endl;
190     for(int i=0;i<ans.size();++i)
191         if(abs(ans[i].d-0)>0.01)
192             cout<<ans[i].x<<" "<<ans[i].y<<" "<<ans[i].d<<endl;
193     return 0;
194 }