#include<bits/stdc++.h>
using namespace std;

typedef long long ll;
const int maxn=4e5+10;
const ll llinf=0x3f3f3f3f3f3f3f3f;

inline int read(){
    int x=0,w=1;char c=getchar();
    while(c<'0'||c>'9'){if(c=='-')w=-1;c=getchar();}
    while(c<='9'&&c>='0'){x=(x<<3)+(x<<1)+c-'0';c=getchar();}
    return x*w;
}

int n;
struct edge{
    int to,nxt,w;
}E1[maxn<<1],E2[maxn<<1],e1[maxn<<2],e2[maxn<<1];
int Head1[maxn],Cnt1,Head2[maxn],Cnt2,head1[maxn<<1],cnt1,head2[maxn],cnt2;
inline void add_edge(edge *e,int *head,int &cnt,int u,int v,int w){
    e[++cnt].to=v,e[cnt].nxt=head[u],head[u]=cnt,e[cnt].w=w;
    e[++cnt].to=u,e[cnt].nxt=head[v],head[v]=cnt,e[cnt].w=w;
}

int tot;
int fa1[maxn<<1],dep1[maxn<<1],siz1[maxn<<1],son1[maxn<<1];
ll dis1[maxn<<1];
int top1[maxn<<1];
void rebuild(int u,int f){
    for(int i=Head1[u],j=0,last=u,v,w;i;i=E1[i].nxt){
        v=E1[i].to,w=E1[i].w;
        if(v==f) continue;
        ++j;
        if(j==1){
            add_edge(e1,head1,cnt1,u,v,w);
        }
        else{
            ++tot;
            add_edge(e1,head1,cnt1,last,tot,0);
            add_edge(e1,head1,cnt1,tot,v,w);
            last=tot;
        }
    }
    for(int i=Head1[u],v;i;i=E1[i].nxt){
        v=E1[i].to;
        if(v==f) continue;
        rebuild(v,u);
    }
}
void dfs1(int u,int f,int d){
    fa1[u]=f,dep1[u]=d,siz1[u]=1;
    for(int i=head1[u],v,w;i;i=e1[i].nxt){
        v=e1[i].to,w=e1[i].w;
        if(v==f) continue;
        dis1[v]=dis1[u]+w;
        dfs1(v,u,d+1);
        siz1[u]+=siz1[v];
        if(!son1[u]||siz1[v]>siz1[son1[u]]) son1[u]=v;
    }
}
void dfs2(int u,int t){
    top1[u]=t;
    if(!son1[u]) return;
    dfs2(son1[u],t);
    for(int i=head1[u],v;i;i=e1[i].nxt){
        v=e1[i].to;
        if(v==fa1[u]||v==son1[u]) continue;
        dfs2(v,v);
    }
}
inline int get_LCA1(int u,int v){
    while(top1[u]!=top1[v]){
        if(dep1[top1[u]]>dep1[top1[v]]) swap(u,v);
        v=fa1[top1[v]];
    }
    if(dep1[u]>dep1[v]) swap(u,v);
    return u;
}


int fa2[maxn],dep2[maxn],siz2[maxn],son2[maxn];
ll dis2[maxn];
int top2[maxn],dfn2[maxn],dfncnt2;
void dfs3(int u,int f,int d){
    fa2[u]=f,dep2[u]=d,siz2[u]=1;
    for(int i=Head2[u],v,w;i;i=E2[i].nxt){
        v=E2[i].to,w=E2[i].w;
        if(v==f) continue;
        dis2[v]=dis2[u]+w;
        dfs3(v,u,d+1);
        siz2[u]+=siz2[v];
        if(!son2[u]||siz2[v]>siz2[son2[u]]) son2[u]=v;
    }
}
void dfs4(int u,int t){
    top2[u]=t,dfn2[u]=++dfncnt2;
    if(!son2[u]) return;
    dfs4(son2[u],t);
    for(int i=Head2[u],v;i;i=E2[i].nxt){
        v=E2[i].to;
        if(v==fa2[u]||v==son2[u]) continue;
        dfs4(v,v);
    }
}
inline int get_LCA2(int u,int v){
    while(top2[u]!=top2[v]){
        if(dep2[top2[u]]>dep2[top2[v]]) swap(u,v);
        v=fa2[top2[v]];
    }
    if(dep2[u]>dep2[v]) swap(u,v);
    return u;
}

ll ans;

vector<int> V;
int st[maxn],top;
ll mx[maxn][2];
inline void build(){
    sort(V.begin(),V.end(),[&](int A,int B){
        return dfn2[A]<dfn2[B];
    });
    V.erase(unique(V.begin(),V.end()),V.end());
    cnt2=0;
    head2[1]=0;
    st[top=1]=1;
    for(int u:V){
        if(u==1) continue;
        if(get_LCA2(u,st[top])==st[top]){
            head2[u]=0;
            st[++top]=u;
            continue;
        }
        while(top>1&&dep2[get_LCA2(u,st[top])]<dep2[st[top-1]]){
            add_edge(e2,head2,cnt2,st[top-1],st[top],0);
            --top;
        }
        if(get_LCA2(u,st[top])==st[top-1]){
            add_edge(e2,head2,cnt2,st[top-1],st[top],0);
            head2[u]=0;
            st[top]=u;
        }
        else{
            int lca=get_LCA2(u,st[top]);
            head2[lca]=0,head2[u]=0;
            add_edge(e2,head2,cnt2,lca,st[top],0);
            st[top]=lca,st[++top]=u;
        }
    }
    for(int i=top;i>1;--i){
        add_edge(e2,head2,cnt2,st[i-1],st[i],0);
    }
}
void calc(int u,int f){
    for(int i=head2[u],v;i;i=e2[i].nxt){
        v=e2[i].to;
        if(v==f) continue;
        calc(v,u);
        ans=max({ans,mx[u][0]+mx[v][1]-dis2[u],mx[u][1]+mx[v][0]-dis2[u]});
        mx[u][0]=max(mx[u][0],mx[v][0]),mx[u][1]=max(mx[u][1],mx[v][1]);
        mx[v][0]=-llinf,mx[v][1]=-llinf;
    }
    if(u==1) mx[u][0]=-llinf,mx[u][1]=-llinf;
}

int ct;
bool vis[maxn<<2];
int maxsiz[maxn<<1],sumsiz;
inline void init(int u){
    ct=0;
    sumsiz=siz1[u];
}
void dfs_siz(int u,int f){
    siz1[u]=1;
    for(int i=head1[u],v;i;i=e1[i].nxt){
        v=e1[i].to;
        if(vis[i]||v==f) continue;
        dfs_siz(v,u);
        siz1[u]+=siz1[v];
    }
}
void dfs_ct(int u,int f){
    maxsiz[u]=0;
    for(int i=head1[u],v;i;i=e1[i].nxt){
        v=e1[i].to;
        if(vis[i]||v==f) continue;
        dfs_ct(v,u);
        maxsiz[v]=max(siz1[v],sumsiz-siz1[v]);
        if(!ct||maxsiz[v]<maxsiz[e1[ct].to]) ct=i;
    }
}
void dfsS(int u,int f,int tmp){
    if(u<=n){
        V.push_back(u);
        mx[u][0]=dis1[u]-dis1[get_LCA1(u,tmp)];
    }
    for(int i=head1[u],v;i;i=e1[i].nxt){
        v=e1[i].to;
        if(vis[i]||v==f) continue;
        dfsS(v,u,tmp);
    }
}
void dfsT(int u,int f,int &tmp){
    if(u<=n){
        V.push_back(u);
        mx[u][1]=dis1[u];
        tmp=u;
    }
    for(int i=head1[u],v;i;i=e1[i].nxt){
        v=e1[i].to;
        if(vis[i]||v==f) continue;
        dfsT(v,u,tmp);
    }
}
void solve(int id){
    if(!id) return;
    vis[id]=true,vis[id^1]=true;
    int u=e1[id].to,v=e1[id^1].to;
    if(fa1[u]==v) swap(u,v);
    V.clear();
    int tmp=0;
    dfsT(v,0,tmp);
    if(!tmp) return;
    dfsS(u,0,tmp);
    build();
    calc(1,0);
    dfs_siz(u,0),init(u),dfs_ct(u,0),solve(ct);
    dfs_siz(v,0),init(v),dfs_ct(v,0),solve(ct);
    
}

int main(){
    n=read();
    for(int i=1,u,v,w;i<n;++i){
        u=read(),v=read(),w=read();
        add_edge(E1,Head1,Cnt1,u,v,w);
    }
    for(int i=1,u,v,w;i<n;++i){
        u=read(),v=read(),w=read();
        add_edge(E2,Head2,Cnt2,u,v,w);
    }
    tot=n,cnt1=1;
    rebuild(1,0);
    dfs1(1,0,0);
    dfs2(1,1);
    dfs3(1,0,0);
    dfs4(1,1);
    ans=-llinf;
    for(int i=1;i<=n;++i) mx[i][0]=mx[i][1]=-llinf;
    dfs_siz(1,0),init(1),dfs_ct(1,0),solve(ct);
    for(int i=1;i<=n;++i) ans=max(ans,dis1[i]-dis2[i]);
    printf("%lld\n",ans);
    return 0;
}