#include<bits/stdc++.h>
using namespace std;
const int N = 200010;
vector <pair <int, int>> g[N];
int dp[N][2][2];
const int inf = 2e9;
void dfs(int v, int f1, int f2, int p){
if(dp[v][f1][f2] != -1) return;
for(auto [x, w] : g[v]){
if(x == p) continue;
dfs(x, 0, 0, v);
dfs(x, 0, 1, v);
dfs(x, 1, 0, v);
dfs(x, 1, 1, v);
}
if(f1 == 0 and f2 == 0){
dp[v][f1][f2] = 0;
int sum = 0, sum2 = 0, best1 = -inf, best2 = -inf;
for(auto [x, w] : g[v]){
if(x == p) {
if(w > best1){
best2 = best1;
best1 = w;
}
else if(w > best2){
best2 = w;
}
continue;
}
sum += dp[x][0][0];
sum2 += dp[x][1][0];
if(best1 < dp[x][1][1]+w-dp[x][1][0]){
best2 = best1;
best1 = dp[x][1][1]+w-dp[x][1][0];
}
else if(best2 < dp[x][1][1]+w-dp[x][1][0]){
best2 = dp[x][1][1]+w-dp[x][1][0];
}
}
dp[v][f1][f2] = sum;
if(best2 != -inf) dp[v][f1][f2] = max(dp[v][f1][f2], sum2+best1+best2);
return;
}
if(f1 == 1 and f2 == 0){
dp[v][f1][f2] = 0;
int sum = 0, sum2 = 0, best1 = -inf, best2 = -inf;
for(auto [x, w] : g[v]){
if(x == p) {
best2 = w;
continue;
}
sum += dp[x][0][0];
sum2 += dp[x][1][0];
if(best1 < dp[x][1][1]+w-dp[x][1][0]){
best1 = dp[x][1][1]+w-dp[x][1][0];
}
}
dp[v][f1][f2] = sum;
if(best2 != -inf and best1 != -inf) dp[v][f1][f2] = max(dp[v][f1][f2], sum2+best1+best2);
return;
}
if(f1 == 0 and f2 == 1){
dp[v][f1][f2] = 0;
int sum = 0, sum2 = 0, best1 = -inf, best2 = -inf;
for(auto [x, w] : g[v]){
if(x == p) {
continue;
}
sum += dp[x][0][0];
sum2 += dp[x][1][0];
if(best1 < dp[x][1][1]+w-dp[x][1][0]){
best2 = best1;
best1 = dp[x][1][1]+w-dp[x][1][0];
}
else if(best2 < dp[x][1][1]+w-dp[x][1][0]){
best2 = dp[x][1][1]+w-dp[x][1][0];
}
}
dp[v][f1][f2] = sum;
if(best2 != -inf) dp[v][f1][f2] = max(dp[v][f1][f2], sum2+best1+best2);
return;
}
dp[v][f1][f2] = 0;
int sum = 0, sum2 = 0, best1 = -inf, best2 = -inf;
for(auto [x, w] : g[v]){
if(x == p) {
continue;
}
sum += dp[x][0][0];
sum2 += dp[x][1][0];
if(best1 < dp[x][1][1]+w-dp[x][1][0]){
best2 = best1;
best1 = dp[x][1][1]+w-dp[x][1][0];
}
else if(best2 < dp[x][1][1]+w-dp[x][1][0]){
best2 = dp[x][1][1]+w-dp[x][1][0];
}
}
dp[v][f1][f2] = sum;
if(best2 != -inf) dp[v][f1][f2] = max(dp[v][f1][f2], sum2+best1+best2);
return;
}
int main(){
memset(dp, -1, sizeof dp);
int n;
cin >> n;
for(int i = 1;i < n;i++){
int a, b, w;
cin >> a >> b >> w;
g[a].push_back({b, w});
g[b].push_back({a, w});
}
dfs(1, 0, 1, 1);
cout << dp[1][0][1] << '\n';
}
