#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
int n,m;
const int N = 3e5+10,M = 1e6+10;
int h[N],e[M],ne[M],w[M],idx;
int max1[N],max2[N],dist[N];//dist?\xbb\xa4?\xc3\xe6·\xbe\xb6\xb5\xc4\xd7\xeeС?\xbe\xb1·
int dist1[N];
int ans[N];
bool st[N];

void add(int a,int b,int c){
    w[idx]=c;
    e[idx]=b;
    ne[idx]=h[a];
    h[a]=idx++;
}

//并查集
int pre[N];
void init(){
    for(int i=1;i<=n;i++) pre[i]=i;
}
int find(int x){
    if(pre[x]!=x) pre[x]=find(pre[x]);
    return pre[x];
}
bool merge(int x,int y){
    int px=find(x),py=find(y);
    if(px!=py){
        pre[px]=py;
        return 1;
    }
    return 0;
}


typedef pair<int, int> PII;
void dij1(){//\xc7\xf3\xd7\xee\xb6\xcc?\xbe\xb1·
    memset(dist,0x3f,sizeof dist);
    memset(st,false,sizeof st);
    dist[1]=0;
//    st[1]=true;
    priority_queue<PII, vector<PII>, greater<PII>> pq; 
    pq.push({0,1});
    while(pq.size()){
        PII k=pq.top();
        pq.pop();
        int ver=k.second,distance=k.first;
        if(st[ver]) continue;
        st[ver]=true;

        for(int i=h[ver];i!=-1;i=ne[i]){
            int j=e[i];
//            if(w[i]>dist[j]){
//                dist[j]=w[i];
//                cout<<j<<" "<<dist[j]<<endl;
//                pq.push({dist[j],j});
//            }
			int val=max(dist[ver],w[i]);
//			cout<<j<<" "<<val<<endl;
			if(val<dist[j]){
				dist[j]=val;
//				cout<<j<<" "<<dist[j]<<endl;
				pq.push({dist[j],j});
			}
        }
    }
}

void dij2(){
	memset(dist1,0x3f,sizeof dist1);
    memset(st,false,sizeof st);
    dist1[n]=0;
    priority_queue<PII, vector<PII>, greater<PII>> pq; 
    pq.push({0,n});
    while(pq.size()){
        PII k=pq.top();
        pq.pop();
        int ver=k.second,distance=k.first;
        if(st[ver]) continue;
        st[ver]=true;

        for(int i=h[ver];i!=-1;i=ne[i]){
            int j=e[i];
//            if(w[i]>dist[j]){
//                dist[j]=w[i];
//                cout<<j<<" "<<dist[j]<<endl;
//                pq.push({dist[j],j});
//            }
			int val=max(dist1[ver],w[i]);
//			cout<<j<<" "<<val<<endl;
			if(val<dist1[j]){
				dist1[j]=val;
//				cout<<j<<" "<<dist[j]<<endl;
				pq.push({dist1[j],j});
			}
        }
    }
} 

struct edge{
    int a,b,c;
};

vector<edge> MST;
vector<edge> e1;
int main(){
	memset(h,-1,sizeof h);
    cin>>n>>m;
    int ans1=0x3f3f3f3f;
    while(m--){
        int a,b,c;
        cin>>a>>b>>c;
        e1.push_back({a,b,c});
        if((a==1&&b==n)||(a==n&&b==1)){
        	ans1=c;
		}
        add(a,b,c),add(b,a,c);
    }
    //最大生成树
    sort(e1.begin(),e1.end(),[&](edge x,edge y){
        return x.c>y.c;
    });
    init();
    for(auto x:e1){
        if(merge(x.a,x.b)){
            MST.push_back(x);
        }
    }
//    cout<<"--"<<ans1<<endl;
    dij1();
    dij2();
    int ans=0x3f3f3f3f;
// 	for(int i=2;i<=n-1;i++){
// //		cout<<dist[i]<<"---"<<dist1[i]<<endl;
// 		ans=max(ans,(ll)dist[i]+(ll)dist1[i]);
// 	}
    for(auto x:MST){
        int a=x.a,b=x.b,c=x.c;
        if(dist1[a]<=c&&dist[b]<=c) ans=min(ans,c+max(dist1[a],dist[b]));
        if(dist1[b]<=c&&dist[a]<=c) ans=min(ans,c+max(dist1[b],dist[a]));
    }
	ans1=min(ans1,ans);
	cout<<ans<<endl;
    
}