/*
* Task: apio14_beads
* Lang: C/C++11
* Author: comtalyst
* Site: oj.uz
* Last Update: 31/10/2017
*/
#include <bits/stdc++.h>
//#pragma GCC optimize ("O3")
using namespace std;
/* Note
----------------------------
Learned :
Bugs found & solved :
- bad state definition (many subbugs)
Optimizations :
----------------------------
0 = Void [0],[1]
1 = Core [0]
2 = Halfcore with void [0],[1]
3 = Halfcore with core [0]
Every Core must match with Void+Void or Core+Void
3rd state : can this joints to dad node? (joint = connect by it, not its dad)
*/
#define x first
#define y second
#define umap unordered_map
#define pqueue priority_queue
#define mset multiset
#define mp make_pair
#define mt make_tuple
#define long long long
#define MOD 1000000007
#define MAX (int)1e9
#define MIN (int)-1e9
#define FILEIN_ freopen("__in.txt","r",stdin)
#define FILEOUT_ freopen("__out.txt","w",stdout)
#define FILEIN(text) freopen(text,"r",stdin)
#define FILEOUT(text) freopen(text,"w",stdout)
int data[200005][4][2];
vector<pair<int,int>> adl[200005];
int dp(int x,int f){
int i,y,w,sxc=0,sxc2=0,v;
pair<int,int> mxv01={MIN,MIN},mxv02={MIN,MIN},mxc1={MIN,MIN},mxc2={MIN,MIN},mxd={MIN,MIN},mxv11={MIN,MIN},mxv12={MIN,MIN};
for(i = 0; i < adl[x].size(); i++){
y = adl[x][i].x;
w = adl[x][i].y;
if(y == f) continue;
dp(y,x);
}
for(i = 0; i < adl[x].size(); i++){
y = adl[x][i].x;
w = adl[x][i].y;
if(y == f) continue;
v = max(data[y][0][1],data[y][2][1]+w);
data[x][0][1] += v;
if(max(data[y][0][0],max(data[y][1][0],max(data[y][2][0]+w,data[y][3][0]+w))) -v > mxd.x){
mxd = {max(data[y][0][0],max(data[y][1][0],max(data[y][2][0]+w,data[y][3][0]+w))) -v,y};
}
}
data[x][0][0] = data[x][0][1]+mxd.x;
for(i = 0; i < adl[x].size(); i++){
y = adl[x][i].x;
w = adl[x][i].y;
if(y == f) continue;
v = max(data[y][0][1],data[y][2][1]+w);
data[x][1][0] += v;
data[x][2][0] += v;
data[x][2][1] += v;
data[x][3][0] += v;
if(data[y][0][0]+w -v > mxv01.x){
mxv02 = mxv01;
mxv01 = {data[y][0][0]+w -v,y};
}
else if(data[y][0][0]+w -v > mxv02.x){
mxv02 = {data[y][0][0]+w -v,y};
}
if(data[y][0][1]+w -v > mxv11.x){
mxv12 = mxv11;
mxv11 = {data[y][0][1]+w -v,y};
}
else if(data[y][0][1]+w -v > mxv12.x){
mxv12 = {data[y][0][1]+w -v,y};
}
if(data[y][1][0]+w -v > mxc1.x){
mxc2 = mxc1;
mxc1 = {data[y][1][0]+w -v,y};
}
else if(data[y][1][0]+w -v > mxc2.x){
mxc2 = {data[y][1][0]+w -v,y};
}
}
if(mxv11.y == mxc1.y){
if(mxv11.y == mxv01.y){
data[x][1][0] = data[x][1][0]+max(max(mxv11.x+mxv12.x,max(mxv11.x+mxv02.x,mxv12.x+mxv01.x)),max(mxv11.x+mxc2.x,mxv12.x+mxc1.x));
}
else{
data[x][1][0] = data[x][1][0]+max(max(mxv11.x+mxv12.x,mxv11.x+mxv01.x),max(mxv11.x+mxc2.x,mxv12.x+mxc1.x));
}
}
else{
if(mxv11.y == mxv01.y){
data[x][1][0] = data[x][1][0]+max(max(mxv11.x+mxv12.x,max(mxv11.x+mxv02.x,mxv12.x+mxv01.x)),mxv11.x+mxc1.x);
}
else{
data[x][1][0] = data[x][1][0]+max(max(mxv11.x+mxv12.x,mxv11.x+mxv01.x),mxv11.x+mxc1.x);
}
}
data[x][2][0] += mxv01.x;
data[x][2][1] += mxv11.x;
data[x][3][0] += mxc1.x;
//printf("%d :\n%d %d %d %d\n%d %d %d %d\n",x,mxe1,mxe2,mxd1,mxd2,data[x][0],data[x][1],data[x][2],data[x][4]);
}
main(){
int t,i,j,n,m,x,y,w;
//FILEIN_;
//FILEOUT_;
scanf("%d",&n);
for(i = 1; i < n; i++){
scanf("%d %d %d",&x,&y,&w);
adl[x].emplace_back(y,w);
adl[y].emplace_back(x,w);
}
dp(1,0);
printf("%d\n",max(max(data[1][0][0],data[1][0][1]),data[1][1][0]));
return 0;
}
