#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ff first
#define ss second
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#define N 200005
const ll MOD = 1000000007;
const int INF = 0x3f3f3f3f;
vector<pair<int, int> > adj[N];
ll dp[N][2];
void dfs(int v, int p, int y){
ll mx1 = -100'000'000'000, mx2 = -100'000'000'000;
for(auto& x : adj[v]){
if(x.ff == p) continue;
dfs(x.ff, v, x.ss);
if(dp[x.ff][0] >= dp[x.ff][1]){
dp[v][0] += dp[x.ff][0];
dp[v][1] += dp[x.ff][0];
if(x.ss >= mx1){
mx2 = mx1;
mx1 = x.ss;
} else mx2 = max(mx2, 1LL * x.ss);
} else {
dp[v][0] += dp[x.ff][1];
dp[v][1] += dp[x.ff][1];
ll t = x.ss - dp[x.ff][1] + dp[x.ff][0];
if(t >= mx1){
mx2 = mx1;
mx1 = t;
} else mx2 = max(mx2, t);
}
}
dp[v][0] += max(mx1 + mx2, 0LL);
dp[v][1] += y + mx1;
dp[v][1] = max(dp[v][1], 0LL);
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n;
cin>>n;
for(int i = 1; i < n; ++i){
int a, b, c;
cin>>a>>b>>c;
adj[a].push_back({b, c});
adj[b].push_back({a, c});
}
dfs(1, 0, 0);
cout<<dp[1][0];
}
