#include<bits/stdc++.h>
using namespace std;
int n,m;
vector<pair<int,int> >e[100005];
int dis[100005],dis2[100005];
bool vis[100005]; 
priority_queue<pair<int,int>>q;
void dij(int s){
	memset(dis,0x3f,sizeof(dis));
	memset(dis2,0x3f,sizeof(dis2));
	memset(vis,0,sizeof(vis));
	dis[s]=0;
	q.push({0,s});
	while(q.size()){
		int u=q.top().second;
		q.pop();
		if(vis[u])continue;
		vis[u]=1;
		for(int i=0;i<e[u].size();i++){
			int v=e[u][i].first,w=e[u][i].second;
			if(dis[v]>dis[u]+w){
				dis2[v]=min(dis2[v],dis[v]);
				dis[v]=dis[u]+w;
				q.push({-dis[v],v});
			}
			else if(dis2[v]>dis[u]+w&&dis[u]+w!=dis[v]){
				dis2[v]=dis[u]+w;
				q.push({-dis2[v],v});
			}
		} 
	}
}
int main(){
	cin>>n>>m;
	for(int i=1;i<=m;i++){
		int u,v,w;
		cin>>u>>v>>w;
		e[u].push_back({v,w});
		e[v].push_back({u,w});
	}
	dij(1);
	cout<<dis2[n];
	return 0;
}