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;

typedef pair< int, int > Pi;
struct edge
{
  int to, cost;
};
typedef vector< vector< edge > > Graph;
const int INF = 1 << 30;

vector< int > min_cost;
int Dijkstra(Graph& graph, int s)
{
  min_cost.assign(graph.size(), INF);
  priority_queue< Pi, vector< Pi >, greater< Pi > > que;
  que.push(make_pair(0, s));
  min_cost[s] = 0;
  while(!que.empty()) {
    int now = que.top().second;
    int cost = que.top().first;
    que.pop();
    if(cost > min_cost[now]) continue;
    for(int i = 0; i < graph[now].size(); i++) {
      edge& e = graph[now][i];
      if(cost < e.cost && e.cost < min_cost[e.to]) {
        min_cost[e.to] = e.cost;
        que.push(make_pair(min_cost[e.to], e.to));
      }
    }
  }
  return(-1);
}

int main()
{
  int N, M;
  cin >> N >> M;
  Graph g(N), rg(N);
  for(int i = 0; i < M; i++) {
    int A, B, C;
    cin >> A >> B >> C;
    --A, --B;
    g[A].push_back((edge){B, C});
    rg[B].push_back((edge){A, C});
  }
  Dijkstra(g, 0);
  int ret = -1;
  for(auto& e : rg[N - 1]) {
    if(min_cost[e.to] < INF) {
      ret = max(ret, e.cost);
    }
  }
  cout << ret << endl;
}

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

#define int long long
typedef vector<int>vint;
typedef pair<int,int>pint;
typedef vector<pint>vpint;
#define rep(i,n) for(int i=0;i<(n);i++)
#define reps(i,f,n) for(int i=(f);i<(n);i++)
#define all(v) (v).begin(),(v).end()
#define each(it,v) for(__typeof((v).begin()) it=(v).begin();it!=(v).end();it++)
#define pb push_back
#define fi first
#define se second
template<typename A,typename B>inline void chmin(A &a,B b){if(a>b)a=b;}
template<typename A,typename B>inline void chmax(A &a,B b){if(a<b)a=b;}

const int INF=1001001001001001001ll;

int N,M;
vpint G[100000];
int dist[100000];
signed main(){
    cin>>N>>M;
    vpint lis;
    rep(i,M){
        int a,b,c;
        cin>>a>>b>>c;
        a--;b--;
        G[a].pb(pint(b,c));
        if(b==N-1)lis.pb(pint(a,c));
    }

    fill_n(dist,N,INF);
    dist[0]=0;
    priority_queue<pint,vector<pint>,greater<pint>>que;
    que.push(pint(0,0));
    while(que.size()){
        int v,c;
        tie(c,v)=que.top();
        que.pop();
        if(dist[v]<c)continue;
        if(v==N-1)continue;
        for(auto &e:G[v]){
            if(e.se<c)continue;
            if(dist[e.fi]<=e.se)continue;
            dist[e.fi]=e.se;
            que.push(pint(dist[e.fi],e.fi));
        }
    }

    int ma=-1;
    for(auto &e:lis){
        if(dist[e.fi]>e.se)continue;
        chmax(ma,e.se);
    }
    cout<<ma<<endl;
    return 0;
}

C++: #include<iostream>
#include<vector>
using namespace std;
#define loop(i,a,b) for(int i=a;i<b;i++)
#define rep(i,a) loop(i,0,a)
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<vvi> vvvi;
const int inf=2e9;
#define pb push_back
int main(){
  int n,m;
  cin>>n>>m;
  vvvi cost(n,vvi(n));
  //  rep(i,n)cost[i][n-1]=-1;
  rep(i,m){
    int a,b,c;
    cin>>a>>b>>c;
    a--;b--;
    cost[a][b].pb(c);
    //    if(b==n-1)cost[a][b]=max(cost[a][b],c);
    //else cost[a][b]=min(cost[a][b],c);
  }
  vi used(n);
  vi d(n,inf);
  d[0]=0;
  used[n-1]=true;
  while(1){
    int v=-1;
    rep(i,n)if(!used[i]&&(v==-1||d[i]<d[v]))v=i;
    if(v==-1)break;
    used[v]=true;
    rep(i,n-1)rep(j,cost[v][i].size())if(d[v]<=cost[v][i][j]&&d[i]>cost[v][i][j])d[i]=cost[v][i][j];
  }
  int out=-1;
  rep(i,n-1)rep(j,cost[i][n-1].size())if(d[i]<=cost[i][n-1][j])out=max(out,cost[i][n-1][j]);
  cout<<out<<endl;
  //rep(i,n)cout<<d[i]<<endl;
}