Go: package main

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

const (
	initialBufSize = 100000
	maxBufSize     = 1000000
)

var sc *bufio.Scanner

func initScanner(r io.Reader) *bufio.Scanner {
	buf := make([]byte, initialBufSize)

	sc := bufio.NewScanner(r)
	sc.Buffer(buf, maxBufSize)
	sc.Split(bufio.ScanWords) // bufio.ScanLines
	return sc
}

func main() {
	sc = initScanner(os.Stdin)
	resolve(parseProblem())
}

type graph struct {
	size  int
	edges [][]int
}

func parseProblem() *graph {
	n := scanInt(sc)
	g := &graph{
		size:  n,
		edges: make([][]int, n),
	}
	for i := 0; i < g.size; i++ {
		_ = scanInt(sc)
		k := scanInt(sc)
		g.edges[i] = make([]int, k)
		for j := 0; j < k; j++ {
			g.edges[i][j] = scanInt(sc) - 1
		}
	}
	return g
}

func resolve(g *graph) {
	ds := make([]int, g.size)
	fs := make([]int, g.size)
	time := 0
	for i := 0; i < len(ds); i++ {
		if ds[i] == 0 {
			time++
			time = _dfs(ds, fs, time, g, i)
		}
	}
	for i := 0; i < len(ds); i++ {
		fmt.Println(i+1, ds[i], fs[i])
	}
	return
}

func _dfs(ds, fs []int, time int, g *graph, idx int) int {
	ds[idx] = time
	for _, next := range g.edges[idx] {
		if ds[next] > 0 {
			continue
		}
		time++
		time = _dfs(ds, fs, time, g, next)
	}
	time++
	fs[idx] = time
	return time
}

// snip-scan-funcs
func scanInt(sc *bufio.Scanner) int {
	sc.Scan()
	i, _ := strconv.Atoi(sc.Text())
	return int(i)
}
func scanString(sc *bufio.Scanner) string {
	sc.Scan()
	return sc.Text()
}

C++: #include<iostream>
#include<vector>
#define SIZE 1000000
using namespace std;

struct Stack{
  int line[SIZE];
  int top;
  void init(){
    top = 0;
  }
  bool empty(){
    return top==0;
  }
  void push(int x){
    line[top]=x;
    top ++;
  }
  int pop(){
    if(empty()) return -1;
    top--;
    return line[top];
  }
};
struct Node
{
  vector<int> toList;
  int dt;
  int ft;
};

Stack stack; 
int t; //time

void init(vector<Node>& nodes)
{
  t=0;
  stack.init();
  stack.push(0);
  for(int i=0;i<nodes.size();i++){
    nodes[i].ft=-1;
    nodes[i].dt=-1;
  }
}
void print(vector<Node> nodes)
{
  int n=nodes.size();
  for(int i=0;i<n;i++){
    cout<<i+1<<" "<<nodes[i].ft<<" "<<nodes[i].dt<<endl;
  }
}
void dfs(vector<Node>& nodes)
{ 
  int idx=stack.pop();
  //cout<<idx+1<<":";
  if(idx>=0){
    if(nodes[idx].ft<0){
      //cout<<" find";
      t++;
      nodes[idx].ft=t;
    }
    if(nodes[idx].toList.size()<=0){
      //cout<<" toList.size==0"<<endl;
      t++;
      nodes[idx].dt=t;
      dfs(nodes);
    }
    int count=0;
    for(int i:nodes[idx].toList){
      if(nodes[i].dt<0){
	//cout<<" jumpto "<<i+1<<endl;
	count++;
	stack.push(idx);
	stack.push(i);
	dfs(nodes);
      }
    }
    if(count==0 && nodes[idx].dt<0){
      //cout<<" finish"<<endl;
      t++;
      nodes[idx].dt=t;
      dfs(nodes);
    }
  }else{
    //cout<<"finish dfs"<<endl;
  }
}

int main()
{
  int n,u,k;
  cin>>n;
  vector<Node> nodes(n);
  for(int i=0;i<n;i++){
    cin>>u>>k;
    nodes[i].toList.resize(0);
    for(int j=0;j<k;j++){
      int tmp;
      cin>>tmp;
      nodes[i].toList.push_back(tmp-1);
    }
  }
  init(nodes);
  //print(nodes);

  dfs(nodes);
  print(nodes);
  return 0;
}

C++: #include <bits/stdc++.h>

using namespace std;
typedef long long int ll;
vector<vector<int>>v;
vector<int>atime,btime;

int n;
int nowtime = 1;

void func(int i)
{
    if(atime[i] == 0) 
    {
        atime[i] = nowtime;
        nowtime++;
    }
    else return;
    for(auto x:v[i]) func(x);
    btime[i] = nowtime;
    nowtime++;
}

int main()
{
    int n;
    cin >> n;
    v.resize(n);
    atime.resize(n);
    btime.resize(n);
    for(int i = 0; i < n; i++)
    {
        atime[i]=0;
        btime[i]=0;
        int u,k;
        cin >> u >> k;
        for(int j = 0; j < k; j++)
        {
            int p;
            cin >> p;
            p--;
            v[i].push_back(p);
        }
    }
    for(int i = 0; i < n; i++) func(i);
    for(int i = 0; i < n; i++) cout << i+1 << " " << atime[i] << " " << btime[i] << endl; 
    
}

C++: //ALDS1_11_B:Depth First Search
#include <iostream>
#include <fstream>
#include <stdio.h>
#include <cstdlib>
#include <string>
#include <tuple>
#include <vector>
#include <map>
#include <list>
#include <set>
#include <queue>
#include <stack>
#include <algorithm>
#include <math.h>
#include <random>
#include <time.h>
#include <cassert>
using namespace std;
#define LL_MIN -9223372036854775808
#define LL_MAX 9223372036854775807

vector<int> v[101];
int d[101];
int f[101];
bool already[101];

int t = 1;

void dfs(int now){
    d[now] = t;
    t++;
    already[now] = 1;
    for(int i=0; i<v[now].size(); i++){
        if(!already[v[now][i]]) dfs(v[now][i]);
    }
    f[now] = t;
    t++;
}

int main(){
    int n;
    cin >> n;
    
    for(int i=0; i<n; i++){
        int u,k;
        cin >> u >> k;
        for(int j=0; j<k; j++){
            int tmp;
            cin >> tmp;
            v[u].push_back(tmp);
        }
        already[u] = false;
        sort(v[u].begin(), v[u].end());
    }

    for(int i=1; i<=n; i++){
        if(!already[i]) dfs(i);
    }

    for(int i=1; i<=n; i++){
        cout << i << " " << d[i] << " " << f[i] << endl;
    }
}

C++: #include <iostream>
#include <vector>
#include <algorithm>
#define N 2000

using namespace std;
vector<vector<int> > pa;
vector<vector<int> > ch;
int first[N] = {0};
int second[N] = {0};
int timestamp = 0;
void dfs(int x) {
    if (ch[x].empty()) {
        return;
    } else {
        for (int i = 0; i < ch[x].size(); i++) {
            if (first[ch[x][i]] == 0 && second[ch[x][i]] == 0) {
                timestamp++;
                first[ch[x][i]] = timestamp;
                dfs(ch[x][i]);
                timestamp++;
                second[ch[x][i]] = timestamp;
            }
        }
        return;
    }
}
int main() {
    int n;
    cin >> n;
    int temp = n;
    pa.clear(); pa.resize(N + 5);
    ch.clear(); ch.resize(N + 5);
    while (temp--) {
        int u, k, v;
        cin >> u >> k;
        for (int i = 0; i < k; i++) {
            cin >> v;
            pa[v].push_back(u);
            ch[u].push_back(v);
        }
    }
    int an = 0;
    for (int i = 1; i <= n; i++) {
        if (pa[i].empty()) {
            an = i;
        } else {
            sort(pa[i].begin(), pa[i].end(), less<int>());
        }
        if (ch[i].empty()) {
            ;
        } else {
            sort(ch[i].begin(), ch[i].end());
        }
    }
    timestamp++;
    first[an] = timestamp;
    dfs(an);
    timestamp++;
    second[an] = timestamp;
    for (int i = 1; i <= n; i++) {
        cout << i << ' ' << first[i] << ' ' << second[i] << '\n';
    }
}

// int main(){
//     for (int i = 1 ; i <= n ; i++)
//         if (discovered[i] == -1)
//             dfs(i);
// }
// 
// void dfs(int cur){
//     discovered[cur] = stamp++;
//     for (int i = 0 ; i < pa[cur].size() ; i++)
//         if (discovered[cur] == -1)
//             dfs(pa[cur][i]);
//     visited[cur] = stamp++;
// }