(n,),*e=[[*map(int,s.split())]for s in open(0)]
g=[[]for _ in range(n)]
for u,v,w in e:
  g[u-1]+=(v-1,w),
  g[v-1]+=(u-1,w),
ans=0
d=[[0]for _ in range(n)]
q=[(0,-1,0,0)]
while q:
  p,z,w,s=q.pop()
  if s:
    nz=max(d[p])+w
    d[z]=sorted(d[z]+[nz])[-2:]
    ans=max(ans,sum(d[z]))
    continue
  for v,nw in g[p]:
    if v!=z:
      q+=(v,p,nw,1),(v,p,nw,0),
print(ans)