1 #include<cstdio>
 2 #include<cstring>
 3 #include<cstdlib>
 4 #include<iostream>
 5 #include<vector>
 6 #include<algorithm>
 7 //#pragma comment(linker, "/STACK:36777216,36777216")
 8 using namespace std;
 9 const int maxn=100005;
10 int father[maxn];
11 bool vis[maxn];
12 int indeg[maxn];
13 int ans,n,m;
14 struct no
15 {
16   int next;
17   int sum;
18 };
19 
20 vector<no>tree[maxn];
21 
22 void init(int n){
23     ans=-1;
24     tree[0].clear();
25   for(int i=1;i<=n;i++){
26        father[i]=i;
27        tree[i].clear();
28   }
29   memset(vis,0,sizeof(vis));
30   memset(indeg,0,sizeof(int)*(n+1));
31 }
32 
33 int find(int a)
34 {
35    while(a!=father[a])
36      a=father[a];
37     return a;
38 }
39 void dfs(int pos,int res)
40 {
41      ans=max(ans,res);
42   int len=tree[pos].size();
43     for(int i=0;i<len;i++)
44     {
45       if(vis[tree[pos][i].next]==0)
46       {
47        vis[tree[pos][i].next]=1;
48        dfs(tree[pos][i].next,res+tree[pos][i].sum);
49        vis[tree[pos][i].next]=0;
50       }
51   }
52 }
53 
54 int main()
55 {
56   int i,x,y,aa,bb,cc;
57   bool flag;
58   while(scanf("%d%d",&n,&m)!=EOF)
59   {
60       init(n);
61       flag=0;
62       for(i=1;i<=m;i++){
63       scanf("%d%d%d",&aa,&bb,&cc);
64       indeg[aa]++;
65       indeg[bb]++;
66       tree[aa].push_back((no){bb,cc});   //无向图
67       tree[bb].push_back((no){aa,cc});
68      if(!flag){
69        x=find(aa);
70        y=find(bb);
71       if(x==y) flag=1;
72       else father[y]=x;
73      }
74       }
75       if(flag)printf("YES\n");
76       else{
77          //寻找端点
78           for(int i=1;i<=n;i++)  {
79             if(indeg[i]==1)
80              tree[0].push_back((no){i,0});   //将多源汇集到一点
81           }
82           vis[0]=1;
83         dfs(0,0);
84         printf("%d\n",ans);
85       }
86   }
87  return 0;
88 }