n = gets.to_i
g = Array.new(n) { [] }
(n - 1).times do
  u, v, w = gets.split.map(&:to_i)
  g[u - 1] << [v - 1, w]
  g[v - 1] << [u - 1, w]
end

def dfs(g, seen, now, cost)
  max = [cost, now]
  g[now].each do |nxt, w|
    next if seen[nxt]

    seen[nxt] = true
    res = dfs(g, seen, nxt, cost + w)
    max = res if max[0] < res[0]
  end

  max
end

seen = Array.new(n, false).tap { _1[0] = true }
far1 = dfs(g, seen, 0, 0)[1]

seen.fill(false).tap { _1[far1] = true }
puts dfs(g, seen, far1, 0)[0]