1 /**************************************************************
 2     Problem: 2435
 3     User: Tunix
 4     Language: C++
 5     Result: Accepted
 6     Time:5292 ms
 7     Memory:73348 kb
 8 ****************************************************************/
 9  
10 //BZOJ 2435
11 #include<vector>
12 #include<cstdio>
13 #include<cstring>
14 #include<cstdlib>
15 #include<iostream>
16 #include<algorithm>
17 #define rep(i,n) for(int i=0;i<n;++i)
18 #define F(i,j,n) for(int i=j;i<=n;++i)
19 #define D(i,j,n) for(int i=j;i>=n;--i)
20 #define pb push_back
21 using namespace std;
22 inline int getint(){
23     int v=0,sign=1; char ch=getchar();
24     while(ch<‘0‘||ch>‘9‘){ if (ch==‘-‘) sign=-1; ch=getchar();}
25     while(ch>=‘0‘&&ch<=‘9‘){ v=v*10+ch-‘0‘; ch=getchar();}
26     return v*sign;
27 }
28 const int N=1001000,INF=~0u>>2;
29 typedef long long LL;
30 /******************tamplate*********************/
31  
32 int to[N<<1],nxt[N<<1],head[N],cnt,l[N<<1];
33 void add(int x,int y,int z){
34     to[++cnt]=y; nxt[cnt]=head[x]; head[x]=cnt; l[cnt]=z;
35     to[++cnt]=x; nxt[cnt]=head[y]; head[y]=cnt; l[cnt]=z;
36 }
37 int n,s[N];
38 LL ans;
39  
40 int dfs(int x,int fa){
41     s[x]=1;
42     for(int i=head[x];i;i=nxt[i])
43         if (to[i]!=fa){
44             s[x]+=dfs(to[i],x);
45             ans+=(LL)abs(n-s[to[i]]*2)*l[i];
46         }
47     return s[x];
48 }
49 int main(){
50 #ifndef ONLINE_JUDGE
51     freopen("2435.in","r",stdin);
52     freopen("2435.out","w",stdout);
53 #endif
54     n=getint();
55     F(i,2,n){
56         int x=getint(),y=getint(),z=getint();
57         add(x,y,z);
58     }
59     dfs(1,0);
60     cout <<ans<<endl;
61     return 0;
62 }