#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<int, int>
#define fi first
#define se second
const int mxN=2e5, INF=2e9;
int n, a[mxN];
ll dp[mxN][4];
vector<pii> adj[mxN];
void dfs1(int u, int p) {
for(pii e : adj[u]) {
if(e.fi==p)
continue;
a[e.fi]=e.se;
dfs1(e.fi, u);
}
}
void dfs2(int u, int p) {
int mi1=-1, mi2=-1;
for(pii e : adj[u]) {
if(e.fi==p)
continue;
dfs2(e.fi, u);
dp[u][0]+=max(max(dp[e.fi][0], dp[e.fi][2]), 0LL);
dp[u][3]+=max(max(dp[e.fi][0], dp[e.fi][1]), max(dp[e.fi][2], 0LL));
if(mi1==-1||dp[e.fi][3]-max(max(dp[e.fi][0], dp[e.fi][2]), 0LL)>dp[mi1][3]-max(max(dp[mi1][0], dp[mi1][2]), 0LL)) {
mi2=mi1;
mi1=e.fi;
} else if(mi2==-1||dp[e.fi][3]-max(max(dp[e.fi][0], dp[e.fi][2]), 0LL)>dp[mi2][3]-max(max(dp[mi2][0], dp[mi2][2]), 0LL))
mi2=e.fi;
}
dp[u][1]=mi2==-1?-INF:dp[u][0]-max(max(dp[mi1][0], dp[mi1][2]), 0LL)+dp[mi1][3]-max(max(dp[mi2][0], dp[mi2][2]), 0LL)+dp[mi2][3];
dp[u][2]=mi1==-1?-INF:dp[u][0]-max(max(dp[mi1][0], dp[mi1][2]), 0LL)+dp[mi1][3]+a[u];
dp[u][3]=max(dp[u][1], dp[u][3])+a[u];
// cout << dp[u][0] << " " << dp[u][1] << " " << dp[u][2] << " " << dp[u][3] << " " << u << endl;
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> n;
for(int i=0; i<n-1; ++i) {
int u, v, c;
cin >> u >> v >> c, --u, --v;
adj[u].push_back({v, c});
adj[v].push_back({u, c});
}
dfs1(0, -1);
dfs2(0, -1);
cout << max(dp[0][0], dp[0][1]);
}
