Go: package main

import (
	"fmt"
)

func main() {
	var n int
	fmt.Scan(&n)
	g := make([][]int, n+1)
	for i := 0; i < n; i++ {
		var u,k int
		fmt.Scan(&u)
		fmt.Scan(&k)
		g[u] = make([]int, k)
		for j := 0; j < k; j++ {
			fmt.Scan(&g[u][j])
		}
	}

	d := make([]int, n+1)
	f := make([]int, n+1)
	dfs(&g, &d, &f, 1, 1)

	for i := 1; i <= n; i++ {
		fmt.Printf("%d %d %d\n", i, d[i], f[i])
	}
}

func dfs(g *[][]int, d *[]int, f *[]int, id int, t int) int {
	if (*d)[id] > 0 {
		return t
	}
	(*d)[id] = t
	t += 1
	for i := 0; i < len((*g)[id]); i++ {
		t = dfs(g, d, f, (*g)[id][i], t)
	}
	(*f)[id] = t
	return t+1
}

Python: import abc


class AdjacentGraph:
    """Implementation adjacency-list Graph.
    Beware ids are between 1 and size.
    """
    def __init__(self, size):
        self.size = size
        self._nodes = [[0] * (size+1) for _ in range(size+1)]

    def set_adj_node(self, id_, adj_id):
        self._nodes[id_][adj_id] = 1

    def __iter__(self):
        self._id = 0
        return self

    def __next__(self):
        if self._id < self.size:
            self._id += 1
            return (self._id, self._nodes[self._id][1:])

        raise StopIteration()

    def dfs(self, handler=None):
        stack = [(1, 0)]
        visited = []
        while len(stack) > 0:
            i, j = stack.pop()
            if j == 0:
                if handler:
                    handler.visit(i)
                visited.append(i)
                yield i
            try:
                j = self._nodes[i].index(1, j+1)
                stack.append((i, j))
                if j not in visited:
                    stack.append((j, 0))
            except ValueError:
                if handler:
                    handler.leave(i)


class EventHandler(abc.ABC):
    @abc.abstractmethod
    def visit(self, i):
        pass

    @abc.abstractmethod
    def leave(self, i):
        pass


class Logger(EventHandler):
    def __init__(self, n):
        self.log = [(0, 0)] * n
        self.step = 0

    def visit(self, i):
        self.step += 1
        self.log[i-1] = (self.step, 0)

    def leave(self, i):
        self.step += 1
        (n, m) = self.log[i-1]
        self.log[i-1] = (n, self.step)

    def by_node(self):
        i = 1
        for discover, finish in self.log:
            yield (i, discover, finish)
            i += 1


def run():
    n = int(input())
    g = AdjacentGraph(n)
    log = Logger(n)

    for i in range(n):
        id_, c, *links = [int(x) for x in input().split()]
        for n in links:
            g.set_adj_node(id_, n)

    for i in g.dfs(log):
        pass

    for node in log.by_node():
        print(" ".join([str(i) for i in node]))


if __name__ == '__main__':
    run()

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

import sys

UNVISITED, VISITED_IN_STACK, POPPED_OUT = 0, 1, 2


def generate_adj_matrix(v_info):
    for v_detail in v_info:
        v_adj_list = v_detail[2:]
        assert len(v_adj_list) == int(v_detail[1])
        for each in v_adj_list:
            init_adj_matrix[int(v_detail[0]) - 1][int(each) - 1] = 1
    return init_adj_matrix


def graph_dfs(v_init):
    global time

    # init the first node of overall graph iterations(times >= 1)
    vertex_visit_stack.append(v_init)
    vertex_status_list[v_init] = VISITED_IN_STACK
    vertex_d_time[v_init] += time
    # init end

    while len(vertex_visit_stack) > 1:
        current_vertex = vertex_visit_stack[-1]
        next_vertex = get_adj_vertices(vertex=current_vertex)

        if next_vertex:
            if vertex_status_list[next_vertex] is UNVISITED:
                vertex_status_list[next_vertex] = VISITED_IN_STACK
                time += 1
                vertex_d_time[next_vertex] += time
                vertex_visit_stack.append(next_vertex)
        else:
            vertex_visit_stack.pop()
            vertex_status_list[current_vertex] = POPPED_OUT
            time += 1
            vertex_f_time[current_vertex] += time

    return None


def get_adj_vertices(vertex):
    index = int(vertex) - 1
    for j in range(vertex_num):
        if adj_matrix[index][j]:
            adj_matrix[index][j] = 0
            return j + 1
    return None


def dfs_start():
    global time
    for i in range(vertex_num):
        if vertex_status_list[i + 1] == UNVISITED:
            # print('round', i + 1)
            graph_dfs(v_init=i + 1)
            time += 1


if __name__ == '__main__':
    _input = sys.stdin.readlines()
    vertex_num = int(_input[0])
    vertex_info = list(map(lambda x: x.split(), _input[1:]))
    init_adj_matrix = [[0] * vertex_num for _ in range(vertex_num)]
    # assert len(vertex_info) == vertex_num

    # config length = (vertex_num + 1)
    vertex_visit_stack = [-1]
    vertex_status_list = [UNVISITED] * vertex_num
    vertex_status_list.insert(0, -1)
    vertex_d_time, vertex_f_time = ([0] * (vertex_num + 1) for _ in range(2))

    adj_matrix = generate_adj_matrix(vertex_info)
    # timing start from 1
    time = 1
    dfs_start()
    for k in range(vertex_num):
        print(k + 1, vertex_d_time[k + 1], vertex_f_time[k + 1])

Python: def dfs(i,a,d,f,t):
    if d[i-1]:
        return t
    d[i-1] = t
    t += 1
    for j in a[i-1]:
        t = dfs(j,a,d,f,t)
    f[i-1] = t
    t += 1
    return t
 
if __name__ == "__main__":
    n = int(input())
    a = []
    for i in range(n):
        a.append(list(map(int,input().split()))[2:])
    d = [0]*n
    f = [0]*n
    t = 1
    for i in range(n):
        if d[i] == 0:
            t = dfs(i+1,a,d,f,t)
    for i in range(n):
        print(i+1,d[i],f[i])

Python: """Depth First Search."""

n = int(input())

adj = [None]
for i in range(n):
    adj_i = list(map(int, input().split()[2:]))
    adj.append(adj_i)

# searched or not, number of vertex, discovery time and finishing time
sndf = [None]
for i in range(1, n + 1):
    sndf.append([False, i])

path = []

def dfs(u):
    time = 0
    path.append(u)
    time += 1
    sndf[u].append(time)

    while path:
        u = path[-1]
        if adj[u]:
            v = adj[u].pop(0)
            if not sndf[v][0]:
                time += 1
                sndf[v].append(time)
                path.append(v)
        else:
            path.pop()
            sndf[u][0] = True
            time += 1
            sndf[u].append(time)


dfs(1)

for x in sndf[1:]:
    print(*x[1:])

Python: import sys

n = int(sys.stdin.readline())+1

m = [[0] * n for _ in range(n)]
discover_time = [-1] * n
finish_time = [0] * n
clock = -1

def walk(p):
    global clock
    clock += 1

    for i in range(n):
        if m[p][i]==0: continue
        if discover_time[i]<0:
            discover_time[i] = clock
            clock = walk(i)
            finish_time[i] = clock
            clock +=1

    return clock

m[0] = [1] * n
for i in range(1,n):
    cols = list(map(int, sys.stdin.readline().split()))
    for j in cols[2:]:
        m[i][j]=1

walk(0)

for i in range(1,n):
    print(i,discover_time[i],finish_time[i])

Python: 
# ??±???????????¢?´¢(Depth First Search)

def DFS(n = 1, A = [0], i = 0, d = [0], f = [0], time = 1):
    for j in range(n):
        if A[i][j] == 1 and d[j] == 0:
            time = time + 1
            d[j] = time
            time = DFS(n, A, j, d, f, time)
    time = time + 1
    f[i] = time
    return time

n = int(raw_input())
A = [0] * n
for i in range(n):
    A[i] = [0] * n

for i in range(n):
    value = map(int, raw_input().split())
    u = value[0] - 1
    k = value[1]
    nodes = value[2:]
    for i in range(k):
        v = nodes[i] - 1
        A[u][v] = 1

d = [0] * n
f = [0] * n

time = 0
for i in range(n):
    if d[i] == 0:
        time = time + 1
        d[i] = time
        time = DFS(n, A, i, d, f, time)

for i in range(n):
    print(str(i + 1) + " " + str(d[i]) + " " + str(f[i]))