1 #include <cctype>
 2 #include <cstdio>
 3 #include <algorithm>
 4 #define max(a,b) a<b?b:a
 5 
 6 const int INF=0x3f3f3f3f;
 7 const int MAXN=50010;
 8 
 9 int n,m,ans;
10 
11 int dis[MAXN],vis[MAXN],q[10000000],id[MAXN];
12 
13 struct data {
14     int u,v;
15     int a,b;
16     friend bool operator < (data x,data y) {
17         return x.a<y.a;
18     }
19 };
20 data p[MAXN<<1];
21 
22 struct node {
23     int to;
24     int a,b;
25     int next;
26     node() {}
27     node(int to,int a,int b,int next):to(to),a(a),b(b),next(next) {}
28 };
29 node Edge[MAXN<<2];
30 
31 int head[MAXN],tot;
32 
33 inline void read(int&x) {
34     int f=1;register char c=getchar();
35     for(x=0;!isdigit(c);c==‘-‘&&(f=-1),c=getchar());
36     for(;isdigit(c);x=x*10+c-48,c=getchar());
37     x=x*f;
38 }
39 
40 inline void swap(int&a,int&b) {int t=a;a=b;b=t;}
41 
42 inline void add(int x,int y,int a,int b) {
43     Edge[++tot]=node(y,a,b,head[x]);
44     head[x]=tot;
45     Edge[++tot]=node(x,a,b,head[y]);
46     head[y]=tot;
47 }
48 
49 int hh() {
50     freopen("magicalforest.in","r",stdin);
51     freopen("magicalforest.out","w",stdout);
52     read(n);read(m);
53     for(int i=1;i<=m;++i) read(p[i].u),read(p[i].v),read(p[i].a),read(p[i].b);
54     std::sort(p+1,p+1+m);
55     for(int i=2;i<=n;++i) dis[i]=INF;
56     ans=INF;
57     for(int i=1;i<=m;++i) {
58         add(p[i].u,p[i].v,p[i].a,p[i].b);
59         int h=0,tail=2;
60         q[1]=p[i].u;
61         q[2]=p[i].v;
62         vis[q[1]]=i;
63         vis[q[2]]=i;
64         while(h<tail) {
65             int u=q[++h];
66             vis[u]=0;
67             for(int j=head[u];j;j=Edge[j].next) {
68                 int v=Edge[j].to;
69                 int t=max(dis[u],Edge[j].b);
70                 if(dis[v]>t) {
71                     dis[v]=t;
72                     if(vis[v]!=i) q[++tail]=v,vis[v]=i;
73                 }
74             }
75         }
76         if(p[i].a+dis[n]<ans) ans=p[i].a+dis[n];
77     }
78     if(ans==INF) printf("-1\n");
79     else printf("%d\n",ans);
80     return 0;
81 } 
82 
83 int sb=hh();
84 int main(int argc,char**argv) {;}