1 #include<cstdio>
 2 #include<algorithm>
 3 #include<cstring>
 4 
 5 using namespace std;
 6 
 7 const int MAXN = 50010;
 8 struct Edge{
 9     int to,nxt,w;
10 }e[500100];
11 int head[MAXN],dp[MAXN];
12 bool vis[MAXN];
13 int n,m,tot,ans;
14 char s[5];
15 
16 inline void init()
17 {
18     memset(vis,false,sizeof(vis));
19     memset(dp,0,sizeof(dp));
20     memset(head,0,sizeof(head));
21     tot = 0;
22     ans = 0;
23 }
24 inline void add_edge(int u,int v,int w)
25 {
26     e[++tot].to = v;e[tot].w = w;e[tot].nxt = head[u];
27     head[u] = tot;
28     e[++tot].to = u;e[tot].w = w;e[tot].nxt = head[v];
29     head[v] = tot;
30 }
31 void dfs(int u)
32 {
33     vis[u] = true;
34     for (int i=head[u]; i; i=e[i].nxt)
35     {
36         int v = e[i].to,w = e[i].w;
37         if (!vis[v])
38         {
39             dfs(v);
40             ans = max(ans,dp[u]+w+dp[v]);
41             dp[u] = max(dp[u],dp[v]+w);
42         }
43     }
44 }
45 int main()
46 {
47     while (~scanf("%d%d",&n,&m))
48     {
49         init();
50         for (int x,y,z,i=1; i<=m; ++i)
51         {
52             scanf("%d%d%d%s",&x,&y,&z,s);
53             add_edge(x,y,z);
54         }
55         dfs(1);
56         printf("%d\n",ans);
57     }
58     return 0;
59 }