#include<iostream>
#include<queue>
#include<cmath>
#include<cstring>
using namespace std;
#define ll long long
struct node
{
	int d,l;
	bool operator < (const node &a) const
	{
		return l>a.l;
	}
};
priority_queue<node> q;
int dis[5005];
bool vis[5005];
int sdis[5005];
int head[10005];
int cnt=0;
struct edge
{
	int w,to,nxt;
};
edge e[200005];
void ad(int u,int v,int w)
{
	cnt++;
	e[cnt].w=w;
	e[cnt].to=v;
	e[cnt].nxt=head[u];
	head[u]=cnt;
};
int n,m;
int main()
{
	cin>>n>>m;
	int u,v,w;
	memset(head,-1,sizeof(head));
	memset(dis,0x7f7f7f7f,sizeof(dis));
	memset(sdis,0x7f7f7f7,sizeof(sdis));
	memset(vis,0,sizeof(vis));
	for(int i=1;i<=m;i++)
	{
		cin>>u>>v>>w;
		ad(u,v,w);
		ad(v,u,w);
	}
	dis[1]=0;
	vis[1]=0;
	sdis[1]=0;
	q.push(node{1,0});
	while(!q.empty())
	{
		node tmp=q.top();
		q.pop();
		int u=tmp.d;
		int w=tmp.l;
		if(vis[u])
		{
			continue;
		}
		vis[u]=1;
		for(int i=head[u];i!=-1;i=e[i].nxt)
		{
			int tw=e[i].w;
			int t=e[i].to;
			if(dis[t]>dis[u]+tw)
			{
				sdis[t]=dis[t];
				dis[t]=dis[u]+tw;
				q.push(node{t,dis[t]});
			}
			if(dis[u]+tw>dis[t]&&dis[u]+tw<sdis[t])
			{
				sdis[t]=dis[u]+tw;
				q.push(node{t,sdis[t]});
			}
			if(sdis[u]+tw<sdis[t]&&sdis[u]+tw>dis[t])
			{
				sdis[t]=sdis[u]+tw;
				q.push(node{t,sdis[t]});
			}
		}
	}
	cout<<sdis[n]<<endl;
	return 0;
}