Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

type TimeRecord struct {
	discoverTime int
	finishTime   int
}

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)

	n, err := nextInt(sc)
	if err != nil {
		panic(err)
	}

	timeRecordMap := make([]TimeRecord, n)
	childrenMap := make([][]int, n)
	for i := 1; i <= n; i++ {
		node, err := nextInt(sc)
		if err != nil {
			panic(err)
		}
		timeRecordMap[node-1] = TimeRecord{-1, -1}

		childNum, err := nextInt(sc)
		if err != nil {
			panic(err)
		}
		childrenMap[node-1] = make([]int, childNum)
		for j := 0; j < childNum; j++ {
			child, err := nextInt(sc)
			if err != nil {
				panic(err)
			}
			childrenMap[node-1][j] = child
		}
	}

	timer := 1
	for {
		startNode := findStartNode(childrenMap, timeRecordMap)
		if startNode > 0 {
			visit(startNode, &timer, childrenMap, timeRecordMap)
		} else {
			break
		}
	}
	for k, v := range timeRecordMap {
		fmt.Printf("%d %d %d\n", k+1, v.discoverTime, v.finishTime)
	}
}

func findStartNode(childrenMap [][]int, timeRecordMap []TimeRecord) int {
	x := -1
	for node, timeRecord := range timeRecordMap {
		if timeRecord.discoverTime < 0 {
			x = node + 1
			break
		}
	}
	if x < 0 {
		return -1
	}

	found := false
	i := 0
	for i < len(childrenMap) {
		children := childrenMap[i]
		for j := 0; j < len(children); j++ {
			if children[j] == x {
				x = j + 1
				found = true
				break
			}
		}
		if found {
			i = 0
		} else {
			i++
		}
	}
	return x
}

func visit(currentNode int, timer *int, childrenMap [][]int, timeRecordMap []TimeRecord) {
	if timeRecordMap[currentNode-1].discoverTime > 0 {
		return
	}
	children := childrenMap[currentNode-1]
	timeRecordMap[currentNode-1] = TimeRecord{*timer, timeRecordMap[currentNode-1].finishTime}
	(*timer)++
	for i := 0; i < len(children); i++ {
		visit(children[i], timer, childrenMap, timeRecordMap)
	}
	timeRecordMap[currentNode-1] = TimeRecord{timeRecordMap[currentNode-1].discoverTime, *timer}
	(*timer)++
}

func nextInt(sc *bufio.Scanner) (int, error) {
	sc.Scan()
	return strconv.Atoi(sc.Text())
}

Python: from enum import Enum


class Dfs(object):
    """ Depth First Search """
    class Status(Enum):
        white = 1
        gray = 2
        black = 3

    def __init__(self, data):
        self.time = 0
        num_of_nodes = len(data)+1
        self.color = [Dfs.Status.white] * (num_of_nodes+1)
        self.S = []
        self.M = self._make_matrix(data)
        self.s_time = [0] * (len(data) + 1)
        self.f_time = [0] * (len(data) + 1)

    def _make_matrix(self, data):
        """ ??£??\??????????????? (M[i][j]?????¢??§??????????????????+1??????????????????????????????) """
        num = len(data)
        graph_table = [[0] * (num+1) for _ in range(num+1)]
        for d in data:
            node_id = d[0]
            num_of_e = d[1]
            for e in d[2:]:
                graph_table[node_id][e] = 1
        return graph_table

    def search(self, start):
        self.time += 1
        self.s_time[start] = self.time
        self.S.append(start)
        self.color[start] = Dfs.Status.gray

        while self.S:
            u = self.S[-1]
            v = self.next(u)
            if v != None:
                if self.color[v] == Dfs.Status.white:
                    self.color[v] = Dfs.Status.gray
                    self.time += 1
                    self.s_time[v] = self.time
                    self.S.append((v))
            else:
                self.S = self.S[:-1]
                self.color[u] = Dfs.Status.black
                self.time += 1
                self.f_time[u] = self.time

    def next(self, node):
        """ ?¬?????¨???????????±???????????????????????????????????????????????¨??????????????????????????????? """
        edges = self.M[node]
        for i in range(1, len(edges)):
            if edges[i] == 1:
                if self.color[i] == Dfs.Status.white:
                    return i
        return None

    def print(self):
        for r in self.M:
            print(*r)


if __name__ == '__main__':
    # ??????????????\???
    num = int(input())
    data = []
    for _ in range(num):
        data.append(list(map(int, input().split(' '))))

    # ???????????????
    d = Dfs(data)
    for i in range(1, num+1):
        if d.color[i] == Dfs.Status.white:
            d.search(i)

    # ???????????????
    for i in range(1, num+1):
        print('{0} {1} {2}'.format(i, d.s_time[i], d.f_time[i]))

Python: #!/usr/bin/env python
# -*- coding: utf-8 -*-

"""

input:
6
1 2 2 3
2 2 3 4
3 1 5
4 1 6
5 1 6
6 0

output:
1 1 12
2 2 11
3 3 8
4 9 10
5 4 7
6 5 6

"""
import sys

UNVISITED, VISITED_IN_STACK, POPPED_OUT = 0, 1, 2


def dfs(v_init):
    global timer

    # init the first node of overall graph iterations(times >= 1)
    stack = list()
    stack.append(v_init)
    d_time[v_init] += timer
    # init end

    while stack:
        current = stack[-1]
        v_table = adj_table[current]
        visited[current] = VISITED_IN_STACK
        # if adj is None, current's adj(s) have been all visited
        adj = v_table.pop() if v_table else None

        if adj:
            if visited[adj] is UNVISITED:
                visited[adj] = VISITED_IN_STACK
                timer += 1
                d_time[adj] += timer
                stack.append(adj)
        else:
            stack.pop()
            visited[current] = POPPED_OUT
            timer += 1
            f_time[current] += timer

    return None


def dfs_init():
    global timer
    for v in range(v_num):
        if visited[v + 1] == UNVISITED:
            dfs(v + 1)
            timer += 1


if __name__ == '__main__':
    _input = sys.stdin.readlines()
    v_num = int(_input[0])
    vertices = map(lambda x: x.split(), _input[1:])

    # config length = (v_num + 1)
    # stack = []
    visited = [UNVISITED] * (v_num + 1)
    d_time, f_time = ([0] * (v_num + 1) for _ in range(2))
    adj_table = tuple([] for _ in range(v_num + 1))
    for v_info in vertices:
        v_index, adj_num, *adj_list = map(int, v_info)
        # assert len(adj_list) == adj_num
        adj_table[v_index].extend(sorted(adj_list, reverse=True))

    # timing start from 1
    timer = 0
    dfs_init()

    for index, time_info in enumerate(zip(d_time[1:], f_time[1:]), 1):
        print(index, *time_info)

Python: # -*- coding: utf-8 -*-

import sys
sys.setrecursionlimit(10 ** 9)
def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
INF=float('inf')

N=INT()
nodes=[[] for i in range(N)]
for i in range(N):
    l=LIST()
    u=l[0]
    l=l[2:]
    for v in l:
        nodes[u-1].append(v-1)
    nodes[u-1].sort()

ans=[[0]*2 for i in range(N)]
visited=[False]*N
time=0
def rec(u):
    if visited[u]:
        return
    visited[u]=True
    global time
    time+=1
    ans[u][0]=time
    for v in nodes[u]:
        rec(v)
    time+=1
    ans[u][1]=time

rec(0)
for i in range(N):
    d,f=ans[i]
    print(i+1, d, f)

Python: #!/usr/bin/python3

def find(A, id, V, time):
    i = id - 1
    A[i][0] = True
    A[i][1] = time
    time += 1
    for v in V[i]:
        if A[v - 1][0] == False:
            time = find(A, v, V, time)
    A[i][2] = time
    time += 1
    return time

n = int(input())
# [isFind, d, f]
A = [[False, 0, 0] for i in range(n)]
U = []
V = []
for i in range(n):
    l = list(map(int, input().split()))
    U.append(l[0])
    V.append(l[2:])

time = 1
for u in U:
    if A[u - 1][0] == False:
        time = find(A, u, V, time)

for u in U:
    l = [u]
    l.extend(A[u - 1][1:])
    print(' '.join(map(str, l)))