import sys
input = sys.stdin.readline
N = int(input())
G = [[] for _ in range(N)]
for i in range(N-1):
    u, v, w = map(int, input().split())
    u-=1
    v-=1
    G[u].append((v, w))
    G[v].append((u, w))

def dfs(v, p):
    ret = [0, 0]
    for nv, w in G[v]:
        if nv==p:
            continue
        tmp = dfs(nv, v)
        ret.append(tmp+w)
    ret.sort(reverse=True)
    dist[v] = ret[:2]
    return ret[0]
dist = [[0, 0] for _ in range(N)]
tmp = dfs(0, -1)
ans = 0
#print(tmp)
#print(dist)
for i in range(N):
    ans = max(ans, sum(dist[i]))
print(ans)