1 #include<iostream>
 2 #include<cstdlib>
 3 #include<cstdio>
 4 #include<cstring>
 5 #include<algorithm>
 6 #include<map>
 7 #include<queue>
 8 #include<string>
 9 #include<cmath>
10 using namespace std;
11 int n,m,zz,a[500005];
12 struct ro{
13     int to,from;
14     int next;
15     int a,b;
16 }road[2000005];
17 struct no{
18     int a,b,from,to;
19 }node[200004];
20 void build(int x,int y,int z,int zx)
21 {
22     zz++;
23     road[zz].from=x;
24     road[zz].to=y;
25     road[zz].next=a[x];
26     road[zz].a=z;
27     road[zz].b=zx;
28     a[x]=zz;
29 }
30 int dis[500005];
31 queue<int> q1;
32 bool rd[500005];
33 int ans=0x7fffffff;
34 void spfa(int x0,int y0,int z,int zx){
35     rd[x0]=rd[y0]=1;
36     q1.push(x0);
37     q1.push(y0);
38     while(!q1.empty())
39     {
40         int x=q1.front();
41         q1.pop();
42         rd[x]=0;
43         for(int i=a[x];i>0;i=road[i].next)
44         {
45             int y=road[i].to;
46
47             if(dis[y]>max(dis[x],road[i].b))
48             {
49                 dis[y]=max(dis[x],road[i].b);
50                 if(!rd[y])
51                 {
52                     q1.push(y);
53                     rd[y]=1;
54                 }
55             }
56         }
57     }
58     int an=0;
59     an=dis[n];
60     if(an!=dis[0]&&ans>an+z)
61         ans=an+z;
62 }
63 int px(no a,no b)
64 {
65     return a.a<b.a;
66 }
67 int main(){
68     memset(dis,0x7f,sizeof(dis));
69     scanf("%d%d",&n,&m);
70     for(int i=1;i<=m;i++)
71     {
72         int x,y,z,zx;
73         scanf("%d%d%d%d",&x,&y,&z,&zx);
74         node[i].a=z;
75         node[i].b=zx;
76         node[i].to=y;
77         node[i].from=x;
78     }
79     sort(node+1,node+m+1,px);
80     dis[1]=0,rd[1]=1;
81     q1.push(1);
82     for(int i=1;i<=m;i++)
83     {
84         int bj=i;
85         build(node[i].from,node[i].to,node[i].a,node[i].b);
86         build(node[i].to,node[i].from,node[i].a,node[i].b);
87         spfa(node[i].from,node[i].to,node[i].a,node[i].b);
88     }
89     if(ans==0x7fffffff) ans=-1;
90     printf("%d\n",ans);
91 //    while(1);
92     return 0;
93 }