#include<bits/stdc++.h> using namespace std; using Int = long long; template<typename T1,typename T2> inline void chmin(T1 &a,T2 b){if(a>b) a=b;} template<typename T1,typename T2> inline void chmax(T1 &a,T2 b){if(a<b) a=b;} template<typename F> struct FixPoint : F{ FixPoint(F&& f):F(forward<F>(f)){} template<typename... Args> decltype(auto) operator()(Args&&... args) const{ return F::operator()(*this,forward<Args>(args)...); } }; template<typename F> inline decltype(auto) MFP(F&& f){ return FixPoint<F>{forward<F>(f)}; } //INSERT ABOVE HERE signed main(){ Int n; cin>>n; using P = pair<Int, Int>; vector< vector< P > > G(n); for(Int i=1;i<n;i++){ Int u,v,w; cin>>u>>v>>w; u--;v--; G[u].emplace_back(v,w); G[v].emplace_back(u,w); } Int ans=0; vector<Int> sz(n,0); MFP([&](auto dfs,Int v,Int p)->void{ sz[v]=1; for(auto e:G[v]){ Int u,c; tie(u,c)=e; if(u==p) continue; dfs(u,v); sz[v]+=sz[u]; ans+=(n-sz[u])*sz[u]*c*2; } })(0,-1); cout<<ans<<endl; return 0; }