Go: package main

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

var scanner = bufio.NewScanner(os.Stdin)

func nextString() string {
	scanner.Scan()
	return scanner.Text()
}

func nextInt() int {
	n, err := strconv.Atoi(nextString())
	if err != nil {
		fmt.Printf("strconv.Atoi failed: %v\n", err)
	}
	return n
}

var infty = 1000000000

type nodeKey int

type DirectedGraphNode struct {
	key       nodeKey
	adjacents []*DirectedGraphNode
	visited   bool
	d         int
	f         int
	parent    *DirectedGraphNode
}

type DirectedGraph struct {
	nodes []*DirectedGraphNode
}

func (g *DirectedGraph) setAdjacency(l, r nodeKey) {
	g.nodes[l].adjacents = append(g.nodes[l].adjacents, g.nodes[r])
}

func newDirectedGraph(nNodes int) *DirectedGraph {
	graph := DirectedGraph{}
	graph.nodes = make([]*DirectedGraphNode, nNodes)
	for iNodes := 0; iNodes < nNodes; iNodes++ {
		graph.nodes[iNodes] = &DirectedGraphNode{}
		graph.nodes[iNodes].key = nodeKey(iNodes)

		graph.nodes[iNodes].visited = false
		graph.nodes[iNodes].d = infty
		graph.nodes[iNodes].f = infty
		graph.nodes[iNodes].parent = nil
	}
	return &graph
}

type QueueEntry struct {
	node *DirectedGraphNode
	next *QueueEntry
}

type Queue struct {
	head, tail *QueueEntry
}

func (q *Queue) enqueue(node *DirectedGraphNode) {
	entry := QueueEntry{}
	entry.node = node

	if q.tail == nil {
		q.head = &entry
		q.tail = &entry
		return
	}

	q.tail.next = &entry
	q.tail = q.tail.next
}

func (q *Queue) dequeue() *QueueEntry {
	if q.head == nil {
		return nil
	}
	poped := q.head
	q.head = q.head.next
	if q.head == nil {
		q.tail = nil
	}
	return poped
}

func (q *Queue) isEmpty() bool {
	return q.head == nil
}

var time = 0

func fillDistancesByDepthFirstSearch(g *DirectedGraph) {
	for _, u := range g.nodes[1:] {
		if !u.visited {
			dfsVisit(g, u)
		}
	}
}

func dfsVisit(g *DirectedGraph, u *DirectedGraphNode) {
	time++
	u.d = time

	u.visited = true
	for _, v := range u.adjacents {
		if !v.visited {
			v.parent = u
			dfsVisit(g, v)
		}
	}
	time++
	u.f = time
}

func main() {
	scanner.Split(bufio.ScanWords)

	nNodes := nextInt()
	g := newDirectedGraph(nNodes + 1)

	for iNode := 0; iNode < nNodes; iNode++ {
		nodeKeyLeft := nodeKey(nextInt())
		nAdj := nextInt()
		for iAdj := 0; iAdj < nAdj; iAdj++ {
			nodeKeyRight := nodeKey(nextInt())
			g.setAdjacency(nodeKeyLeft, nodeKeyRight)
		}
	}

	fillDistancesByDepthFirstSearch(g)

	for iNode := 1; iNode <= nNodes; iNode++ {
		node := g.nodes[iNode]
		fmt.Println(node.key, node.d, node.f)
	}
}

C++: #include <stdio.h>

int time, n;
int d[100], f[100], color[100];
int M[100][100];

void dfs(int u) {
    color[u] = 1;
    d[u] = ++time;
    for (int i=0; i<n; i++) {
        if(M[u][i] && color[i] == 0) {
            dfs(i);
        }
    }
    color[u] = 2;
    f[u] = ++time;
}

void dfs_init(){
    for (int i=0; i<100; i++) color[i] = 0;
    dfs(0);
}

int main() {
    int u, k, v;
    scanf("%d", &n);
    
    for (int i=0; i<n; i++) {
        for (int j=0; j<n; j++) {
            M[i][j] = 0;
        }
    }
    
    for (int i=0; i<n; i++) {
        scanf("%d %d", &u, &k);
        for (int j=0; j<k; j++) {
            scanf("%d", &v);
            M[u-1][v-1] = 1;
        }
    }
    
    dfs_init();
    
    for (int i=0; i<n; i++) {
        printf("%d %d %d\n", i, d[i], f[i]);
    }
    return 0;
}

C++: #include <iostream>
#include <algorithm>
#include <vector>
#include <stack>
#include <sstream>
#include <iomanip>
#include <cmath>
#include <string>
#include <cstdio>
#include <queue>
#include <list>
using namespace std;

int n;

struct Node{
public:
  int id, d, f, flag;
  vector<int> c;
  Node(){d = 1000000007;f = flag = 0;}
};

vector<Node> v(101);

void rec(int id, int &t){
  if(v[id].flag)return;
  else          v[id].flag = 1;
  v[id].d = min(v[id].d, ++t);
  for(int i=0;i<v[id].c.size();i++) {
    rec(v[id].c[i], t);
  }
  v[id].f = max(v[id].f, ++t);
}


bool asc(const Node &right, const Node &left){return right.id < left.id;}

int main(){
  cin >> n;
  
  v[0].id = 0;  
  for(int i=1;i<=n;i++){
    int t, a;  cin >> a >> t;
    vector<int> b(t);
    for(int j=0;j<t;j++){
      int val;cin >> val;
      b[j] = val;
    }
    v[a].id = a;
    v[a].c = b;
  }
  sort(v.begin(), v.end(), asc);

  int ti = 0;
  for(int i=1;i<=n;i++){
    rec(i, ti);
  }

  for(int i=1;i<=n;i++){
    printf("%d %d %d\n", v[i].id, v[i].d, v[i].f);
  }
  return 0;
}

C++: using namespace std;
typedef long long ll;
typedef unsigned long long ull;
#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
#define int long long
#define rep(i,n) for(int i = 0; i < (n); i++)
#define divup(a,b) ( ( (a) + ( (b) - 1u) ) / (b) ) // a/b の余り切り上げ
// #include <boost/multiprecision/cpp_int.hpp>
// using namespace boost::multiprecision;
const ll mod = 1000000007;
const ll mod9 = 1000000009;

ll d[109];
ll f[109];
ll u[109];
ll k[109];
ll v[109][109];
ll t=0;

ll  dfs(ll n){
    if(d[n]==0){
        t++;
        d[n]=t;
    // cout<<" d "<<n<<" "<<t<<endl;
    }

    ll ct=0;
    rep(i,k[n]){
        if(d[v[n][i]-1]==0) dfs(v[n][i]-1),ct++;
    }
    t++;
    f[n]=t;
    // cout<<" f "<<n<<" "<<t<<endl;
    return 0;
}

signed main(){
    ll n;
    cin>>n;
    rep(i,n){
        ll a;
        cin>>u[i]>>k[i];
        rep(j,k[i]){
            cin>>v[i][j];
        }
    }
    rep(i,n){
        if(d[i]==0) dfs(i);
    }
    rep(i,n){
        printf("%lld %lld %lld\n",i+1,d[i],f[i]);
    }
}

C++: 6
1 2 2 3
2 2 3 4
3 1 5
4 1 6
5 1 6
6 0

C++: #include <bits/stdc++.h>
using namespace std;

vector<vector<int>> g;
vector<int> d;
vector<int> f;
int t;

void dfs( int v )
{
	d[v] = ++t;
	for( int u : g[v] ) {
		if( d[u] ) continue;
		dfs( u );
	}
	f[v] = ++t;
}

int main()
{
	int n;
	cin >> n;
	g = vector<vector<int>>( n );
	d = vector<int>( n );
	f = vector<int>( n );
	for( int i = 0; i < n; i++ ) {
		int u, k;
		cin >> u >> k;
		u--;
		for( int j = 0; j < k; j++ ) {
			int v;
			cin >> v;
			v--;
			g[u].push_back( v );
		}
	}

	for( int i = 0; i < n; i++ ) {
		if( d[i] ) continue;
		dfs( i );
	}

	for( int i = 0; i < n; i++ ) {
		cout << i + 1 << " " << d[i] << " " << f[i] <<  endl;
	}
}

C++: #include <iostream>

constexpr int MAXN = 100;
int V[MAXN][MAXN];
int D[MAXN];
int F[MAXN];

template<int STACK_SIZE, typename T = int>
class Stack {

public:
    Stack() {};

    void Push(T val) {
        if (top_ < STACK_SIZE) {
            stack_[top_++] = val;
        }else{
            std::cerr << "Stack over flow..." << std::endl;
            exit(-11);
        }
    };
    bool Pop() {
        if (top_ > 0) {
            stack_[--top_];
            return true;
        }
        return false;
    };

    T Top() {
        return stack_[top_ - 1];
    }

    int Size() {return top_;}


private:
    int max_size_ = STACK_SIZE;
    int top_ = 0;
    T stack_[STACK_SIZE];
};

Stack<MAXN, int> S;

int main() {

    int n;
    std::cin >> n;

    for (int i = 0; i < n; i++) {
        int id, e_num;
        std::cin >> id >> e_num;
        for (int j = 0; j < e_num; j++) {
            int t;
            std::cin >> t;
            V[id - 1][t - 1] = 1;
        }
    }
    int cnt = 0;
    for (int t = 0; t < n; t++) {
        if (D[t] == 0) {
            D[t] = ++cnt;
            S.Push(t);
            while (S.Size()) {
                for (int i = 0; i < n; i++) {
                    if ((V[S.Top()][i] == 1) && (D[i] == 0)) {
                        S.Push(i);
                        D[i] = ++cnt;
                        break;
                    }
                    if (i == n - 1) {
                        F[S.Top()] = ++cnt;
                        S.Pop();
                    }
                }
            }
        }
    }

    for (int i = 0; i < n; i++) {
        std::cout << i + 1 << " " << D[i] << " " << F[i] << std::endl;
    }

}