#include using namespace std; #define int long long using ll=long long; #define P pair #define fi first #define se second #define rep(i,n) for(int i=0;i inline bool chmax(T &a,U b){ if(a inline bool chmin(T &a,U b){ if(a>b){ a=b; return true; } return false; } constexpr int INF=1000000000; constexpr ll llINF=1000000000000000000; constexpr int mod=1000000007; constexpr double eps=1e-8; const double pi=acos(-1); int dx[]={0,1,0,-1},dy[]={1,0,-1,0}; int Random(int mi,int ma){ random_device rnd; mt19937 mt(rnd());//32bit //[mi,ma] uniform_int_distributionengine(mi,ma); return engine(mt); } /* vector>C,sC; void init_comb(int n,int m){ C.resize(n+1,vector(m+1,0)); sC.resize(n+1,vector(m+1,0)); C[0][0]=1; for(int i=1;i<=n;i++){ C[i][0]=1; for(int j=1;j<=m;j++){ C[i][j]=(C[i-1][j-1]+C[i-1][j])%mod; } } rep(i,n+1){ rep(j,m){ sC[i][j+1]=(sC[i][j]+C[i][j])%mod; } } }*/ ll gcd(ll a,ll b){ while(a%b){ a%=b; swap(a,b); } return b; } ll lcm(ll a,ll b){ return a/gcd(a,b)*b; } bool prime(int a){ if(a==1)return false; for(int i=2;i*i<=a;i++){ if(a%i==0)return false; } return true; } ll modpow(ll a,ll b){ ll res=1; while(b){ if(b&1){ res*=a; res%=mod; } a*=a; a%=mod; b>>=1; } return res; } vectorinv,fact,factinv; void init_fact(int n){ inv.resize(n+1); fact.resize(n+1); factinv.resize(n+1); inv[0]=0; inv[1]=1; fact[0]=1; factinv[0]=1; for(ll i=1;i<=n;i++){ if(i>=2)inv[i]=mod-((mod/i)*inv[mod%i]%mod); fact[i]=(fact[i-1]*i)%mod; factinv[i]=factinv[i-1]*inv[i]%mod; } } ll _inv(ll a,ll m=mod){ //gcd(a,m) must be 1 ll b=m,u=1,v=0; while(b){ ll t=a/b; a-=t*b;swap(a,b); u-=t*v;swap(u,v); } u%=m; if(u<0)u+=m; return u; } ll comb(int a,int b){ if(aG[200010]; bool used[200010]; void dfs(int x){ used[x]=true; siz[x]=1; for(edge e:G[x]){ if(!used[e.to]){ dist[e.to]=dist[x]+e.cost; dfs(e.to); siz[x]+=siz[e.to]; } } } void dfs3(int x){ used[x]=true; for(edge e:G[x]){ if(!used[e.to]){ dfs3(e.to); distsum[x]+=(distsum[e.to]+siz[e.to]*e.cost%mod)%mod; distsum[x]%=mod; } } } void dfs2(int x,ll distsum_l=0){ used[x]=true; for(edge e:G[x]){ if(!used[e.to]){ ll distsum_to=(distsum[e.to]+siz[e.to]*e.cost%mod)%mod; ll new_l=(distsum_l+(distsum[x]+mod-distsum_to))%mod; dp[e.to]+=(dp[x]+new_l*2*e.cost%mod)%mod; dp[e.to]%=mod; dp[e.to]-=distsum_to*2*e.cost%mod; dp[e.to]+=mod; dp[e.to]%=mod; dp[e.to]+=e.cost%mod*e.cost%mod*n%mod; dp[e.to]%=mod; new_l+=e.cost*(n-siz[e.to])%mod; new_l%=mod; dfs2(e.to,new_l); } } } signed main(){ cin.tie(0);ios::sync_with_stdio(false); cin>>n; rep(i,n-1){ int a,b,w; cin>>a>>b>>w; a--,b--; G[a].pb({b,w}); G[b].pb({a,w}); } dfs(0); fill(used,used+n,false); dfs3(0); fill(used,used+n,false); rep(i,n){ dp[0]+=dist[i]*dist[i]%mod; dp[0]%=mod; } dfs2(0); ll ans=0; rep(i,n){ ans+=dp[i]; ans%=mod; } cout<