func findNode(from start: Int, of graph: [[(node: Int, weight: Int)]]) -> (node: Int, length: Int) {
    var result = (node: start, length: 0)
    
    var visited = Array(repeating: false, count: graph.count)
    var stack = [(node: Int, length: Int)]()
    stack.append(result)
    visited[start] = true
    
    while !stack.isEmpty {
        if let (now, cur_len) = stack.popLast()
        {
            if cur_len > result.length {
                result = (node: now, length: cur_len)
            }
            
            for next in graph[now] {
                if !visited[next.node] {
                    visited[next.node] = true
                    stack.append((node: next.node, length: cur_len + next.weight))
                }
            }
        }
    }
    
    return result
}

if let N = Int(readLine() ?? "0")
{
    if N == 1 {
        print(0)
    }
    else {
        var graph = Array(repeating: [(node: Int, weight: Int)](), count: N+1)
        
        for _ in 0..<N-1 {
            if let line = readLine(),
               let data = line.split(separator: " ").compactMap({Int($0)}) as? [Int],
               data.count == 3
            {
                let parent = data[0]
                let child = data[1]
                let weight = data[2]
                
                graph[parent].append((node: child, weight: weight))
                graph[child].append((node: parent, weight: weight))
            }
        }
        
        let startNode: Int = findNode(from: 1, of: graph).node
        print(findNode(from: startNode, of: graph).length)
    }
}