func findMaxLenNode(start n: Int, of graph: [[(node: Int, dist: Int)]]) -> (node: Int, dist: Int) {
    var result = (node: n, dist: 0)
    var visited = Array(repeating: false, count: graph.count+1)
    var stack: [(node: Int, dist: Int)] = []
    stack.append(result)
    visited[n] = true
    
    while !stack.isEmpty {
        if let (cur_node, cur_dist) = stack.popLast(){
            
            if cur_dist > result.dist {
                result = (node: cur_node, dist: cur_dist)
            }
            
            for next in graph[cur_node] {
                if !visited[next.node] {
                    stack.append((node: next.node, dist: cur_dist + next.dist))
                    visited[next.node] = true
                }
            }
        }
    }
    
    return result
}


if let V = Int(readLine() ?? "") {
    var tree: [[(node: Int, dist: Int)]] = Array(repeating: [], count: V+1)
    
    for _ in 1...V {
        if let line = readLine(),
           let info = line.split(separator: " ").compactMap({Int($0)}) as? [Int]
        {
            let u = info[0]
            var i = 1
            
            while info[i] != -1 {
                tree[u].append((node: info[i], dist: info[i+1]))
                i += 2
            }
        }
    }
    
    let start = findMaxLenNode(start: 1, of: tree).node
    print(findMaxLenNode(start: start, of: tree).dist)
}