Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
//	"strings"
    "sort"
//    "container/heap"
)

/*********** Input **************/
/*
var rdr = bufio.NewReaderSize(os.Stdin, 1000000)

func readLine() string {
	buf := make([]byte, 0, 1000000)
	for {
		l, p, e := rdr.ReadLine()
		if e != nil {
			panic(e)
		}
		buf = append(buf, l...)
		if !p {
			break
		}
	}
	return string(buf)
}*/

func scanInt(sc *bufio.Scanner) int {
    sc.Scan()
    v, _ := strconv.Atoi(sc.Text())
    return v
}
/**************  End Input  **************/

func toInt(str string) int {
	n, _ := strconv.Atoi(str)
	return n
}

type Edge struct {
	to      int
	newTime int
}

type State struct {
	node int
	time int
}


/**************  Cell  *****************/

type Cell struct {
	item *State
	next *Cell
}

func NewCell(x *State, cp *Cell) *Cell {
	newCp := new(Cell)
	newCp.item = x
	newCp.next = cp
	return newCp
}

/************  End Cell  ***************/

/**************  Queue  ****************/

type Queue struct {
	size  int
	front *Cell
	rear  *Cell
}

func NewQue() *Queue {
	return new(Queue)
}

func (q *Queue) Push(x *State) {
	newNode := NewCell(x, nil)
	if q.size == 0 {
		q.front = newNode
		q.rear = newNode
	} else {
		q.rear.next = newNode
		q.rear = newNode
	}
	q.size++
}

func (q *Queue) PopLeft() (*State, bool) {
	if q.size == 0 {
		return nil, false
	} else {
		x := q.front.item
		q.front = q.front.next
		q.size--
		if q.size == 0 {
			q.rear = nil
		}
		return x, true
	}
}

func (q *Queue) IsEmpty() bool {
	return q.size == 0
}

/***********  end Queue  ***********/

type EdgeSorter struct {
    edges []Edge
    lessfunc []lessFunc
    used int
    length int
}

type lessFunc func(i, j *Edge)bool

func (ES EdgeSorter) Len() int {
    return len(ES.edges)
}

func (ES EdgeSorter) Swap(i, j int) {
    ES.edges[i], ES.edges[j] = ES.edges[j], ES.edges[i]
}

func (ES EdgeSorter) Less(i, j int) bool {
    var k int
    p, q := &ES.edges[i], &ES.edges[j]
    for k=0; k<len(ES.lessfunc)-1;k++ {
        less := ES.lessfunc[k]
        switch {
            case less(p, q):
                return true
            case less(q, p):
                return false
        }
    }
    return ES.lessfunc[k](p, q)
}

/*********** PriorityQueue ***********/
/*
type PriorityQueue struct {
    arr []*State
    size int
}

func (pq PriorityQueue) Len() int {
    return len(pq.arr)
}

func (pq PriorityQueue) Swap(i, j int) {
    pq.arr[i], pq.arr[j] = pq.arr[j], pq.arr[i]
}

func (pq PriorityQueue) Less(i, j int) bool{
    return pq.arr[i].time < pq.arr[j].time
}

func (pq *PriorityQueue) Push(x interface{}) {
    item := x.(*State)
    pq.arr = append(pq.arr, item)
    pq.size++
}

func (pq *PriorityQueue) Pop() interface{} {
    n := pq.size
    item := pq.arr[n - 1]
    pq.arr = pq.arr[:n - 1]
    pq.size--
    return item
}
*/


func main() {
    sc := bufio.NewScanner(os.Stdin)
    sc.Split(bufio.ScanWords)
	n, m := scanInt(sc), scanInt(sc)
	edges := make([]EdgeSorter, 0)
	for i := 0; i < n; i++ {
		edges = append(edges, EdgeSorter{})
	}
	for i := 0; i < m; i++ {
        a, b, c := scanInt(sc) - 1, scanInt(sc) - 1, scanInt(sc)
		edges[a].edges = append(edges[a].edges, Edge{to: b, newTime: c})
	}

    byNewTime := func(p1 *Edge, p2 *Edge) bool{
        return p1.newTime >= p2.newTime
    }

    for i, _ := range edges {
        v := &edges[i]
        v.lessfunc = append(v.lessfunc, byNewTime)
        sort.Sort(v)
        v.used = 0
        v.length = len(v.edges)
    }
    var minTime [100000]int
    for i := 0; i < n; i++ {
        minTime[i] = 2000000000
    }
    minTime[0] = 0
    que := Queue{}
    que.Push(&State{node: 0, time: 0})
	ans := -1
	for !que.IsEmpty() {
		state, _ := que.PopLeft()
		for edges[state.node].used < edges[state.node].length {
            e := edges[state.node].edges[edges[state.node].used]
			if e.newTime >= state.time {
                if e.to == n - 1 && e.newTime > ans {
                    ans = e.newTime
             

C++: #include<bits/stdc++.h>
using namespace std;
#define MAX_N 100001
struct edge{ int to,cost; };
typedef pair<int,int> P;

int N,M;
int d[MAX_N];
vector< edge > G[MAX_N];

int main(){
  cin>>N>>M;
  for(int i=0;i<M;i++){
    int a,b,c;
    scanf("%d %d %d",&a,&b,&c);
    G[a].push_back((edge){b,c});
  }
  
  int ans=-1;  
  priority_queue< P , vector<P> , greater<P> > Q;

  fill(d,d+MAX_N, (1e9+1) );
  Q.push(P(1,1));
  d[1]=1;
  while(!Q.empty()){
    P p=Q.top();Q.pop();
    int pos=p.second;
    int cost=p.first;
    if(d[pos]<cost)continue;
    for(int i=0;i<(int)G[pos].size();i++){
      edge e=G[pos][i];
      if(e.cost<d[pos])continue;
      if(e.to==N)ans=max(ans,e.cost);
      if(d[e.to]>e.cost){
        d[e.to]=e.cost;
        Q.push(P(d[e.to],e.to));
      }
    }
  }

  printf("%d\n",ans);
  return 0;
}

C++: #include<iostream>
#include<utility>
#include<vector>
#define loop(i,a,b) for(int i=a;i<b;i++)
#define rep(i,a) loop(i,0,a)
#define pb push_back
using namespace std;
typedef long long ll;
typedef pair<int,ll> p;
vector<p> dist[100000];
bool used[100000];
int g;
int n,m,a,b;

ll dfs(int i,ll time,ll retime){
	ll res=-1;
	if(i==g)return time;
	else{
		rep(e,dist[i].size()){
			if(!used[dist[i][e].first]){
				used[dist[i][e].first]=true;
				if(retime>dist[i][e].second)continue;
				res=max(res,dfs(dist[i][e].first,time+dist[i][e].second-retime,dist[i][e].second));
				used[dist[i][e].first]=false;
			}
		}
	}
	return res;
}

int main(){
	ll c;
	cin>>n>>m;
	rep(i,m){
		cin>>a>>b>>c;
		dist[a-1].pb(pair<int,ll>(b-1,c));
	}
	g=n-1;
	rep(i,n)used[i]=false;
	used[0]=true;
	cout<<dfs(0,0,0)<<endl;
	return 0;
}

C++: #include<iostream>
#include<utility>
#include<algorithm>
using namespace std;
int c=0;
pair<int,pair<int,int> > p[2000000];
int m;
int tansa(int,int);
int main(){
  int n;

  cin >> n >> m;
  for(int i=0;i<m;i++){
    cin>>p[i].second.second>>p[i].first>>p[i].second.first; 
  }
  sort(p,p+m);
  for(int i=m-1;i>=0;i--){
    if(p[i].first==n){
      int ans;
      if(p[i].second.second==1){
	cout << p[i].second.first << endl;
	return 0;
      }
      ans=tansa(p[i].second.second,p[i].second.first);
      if(c==1000){
	cout << -1 << endl;
	return 0;
      }
      if(ans==-1)continue;
      cout << p[i].second.first << endl;
      return 0;
    }
    else{
      cout << -1 << endl;
      return 0;
    }
  }
  cout << -1 << endl;
  return 0;
}
int tansa(int iru,int time){
  int ans;
  c++;
  if(c==1000)return -1;
  for(int i=m-1;i>=0;i--){
    if(iru==p[i].first&&time>=p[i].second.first){
      if(p[i].second.second==1)return 1;
      
      ans=tansa(p[i].second.second,p[i].second.first);
      if(ans==1){
	
	return 1;
      }
      
      else continue;
    }
  }
  // else if(iru>p[i].first){
  
  return -1;
  //  }
  //}
}

C++: #include<bits/stdc++.h>
#define PB push_back
#define MP make_pair
#define F first
#define S second
#define int long long int
using namespace std;
typedef vector<int> VI;
typedef pair<int, int> PII;
typedef vector<PII> VP;

int n, m;
int a[200010], b[200010], c[200010];
int ans = -1;
VP node[100010];

priority_queue<PII, VP, greater<PII> > q;
int visited[100010];

void dijk()
{
  memset(visited, -1, sizeof visited);
  q.push(MP(0, 1));

  while(!q.empty()){
    PII now = q.top();
    q.pop();
    if(now.S == n){
      ans = max(ans, now.F);
    }
    else if(visited[now.S] == -1){
      visited[now.S] = now.F;

      for(int i = 0; i < node[now.S].size(); i++){
	if(node[now.S][i].F >= now.F){
	  q.push(node[now.S][i]);
	}
      }
    }
  }  
}

signed main()
{
  scanf("%lld%lld", &n, &m);
  for(int i = 0; i < m; i++){
    scanf("%lld%lld%lld", &a[i], &b[i], &c[i]);
    
    node[a[i]].PB(MP(c[i], b[i]));
    node[b[i]].PB(MP(c[i], a[i]));
  }
  
  dijk();

  cout << ans << endl;
  return 0;
}