%:pragma GCC optimize()

 #include<bits/stdc++.h>

 using namespace std;

 const int N=;

 int to[N],fst[N],nxt[N],fa[N],t[N];

 long long dis[N],a[N],b[N],ans=1e13;

 int x,y,aa,bb,tot=,n,m;

 bool vis[N];

 inline void add(int x,int y,int aa,int bb){

     to[++tot]=y; nxt[tot]=fst[x]; fst[x]=tot; a[tot]=aa; b[tot]=bb;

 }

 inline int ask(int x){

     if (fa[x]==x) return x; fa[x]=ask(fa[x]); return fa[x];

 }

 struct cmp{bool operator ()(int a,int b){return dis[a]>dis[b];}};

 priority_queue <int,vector<int>,cmp> q;

 inline void dij(int lim){

     for (int i=;i<=n;++i) dis[i]=1e13;

     memset(vis,,sizeof(vis));

     dis[]=; q.push();

     while (!q.empty()){

         int t=q.top(); q.pop();

         if (vis[t]) continue; vis[t]=;

         for (int i=fst[t];i;i=nxt[i])

             if (a[i]<=lim&&dis[to[i]]>max(dis[t],b[i]))

                 dis[to[i]]=max(dis[t],b[i]),q.push(to[i]);

     }

 }

 int main(){

     scanf("%d%d",&n,&m);

     for (int i=;i<=n;++i) fa[i]=i;

     for (int i=;i<=m;++i){

         scanf("%d %d %d %d",&x,&y,&aa,&bb);

         add(x,y,aa,bb); add(y,x,aa,bb); fa[ask(x)]=ask(y);

     }

     if (ask(fa[])!=ask(fa[n])){

         printf("-1"); return ;

     }

     for (int i=;i<=tot;++i){

         dij(a[i]); ans=min(ans,a[i]+dis[n]);

     }

     if (ans>=1e13) printf("-1");

         else printf("%lld\n",ans);

 }