#include<bits/stdc++.h>
#define N 1000010
using namespace std;
int n,m,s;
int cnt;
int ans;
int numx,numy;
int ver[N],head[N],d[N],nex[N*2],edge[N*2],path[N],f[N];
bool v[N];

priority_queue<pair<int,int> > q;

int read(){
	int x=0,y=1;
	char ch=getchar();
	while(ch>'9'||ch<'0'){
		if(ch=='-') y=-1;
		ch=getchar();
	}
	while(ch<='9'&&ch>='0'){
		x=x*10+ch-'0';
		ch=getchar();
	}
	return x*y;
}

void add_edge(int x,int y,int z){
	ver[++cnt]=y;
	edge[cnt]=z;
	nex[cnt]=head[x];
	head[x]=cnt;
}

void dijkstra(){
	memset(d,0x3f3f3f3f,sizeof(d));
	memset(v,0,sizeof(v));
	d[1]=0;
	//while(q.size()) q.pop();
	q.push(make_pair(0,1));
	while(q.size()){
		int x=q.top().second;
		q.pop();
		if(v[x]) continue;
		v[x]=1;
		for(int i=head[x];i;i=nex[i]){
			int y=ver[i],z=edge[i];
			if((numx==x&&numy==y)||(numx==y&&numy==x)) continue;
			if(d[y]>d[x]+z){
				d[y]=d[x]+z;
				q.push(make_pair(-d[y],y));
				path[y]=x;
			}
		}
	}
}

int main(){
	n=read(); m=read();
	for(int i=1;i<=m;i++){
		int x,y,z;
		x=read(); y=read(); z=read();
		add_edge(x,y,z);
		add_edge(y,x,z);
	}
	dijkstra();
	for(int i=1;i<=n;i++) f[i]=path[i];
	int ff=n;
	while(ff!=0){
		numx=f[ff];
		numy=ff;
		dijkstra();
		ans=max(d[n],ans);
		ff=f[ff];
	}
	cout<<ans<<endl;
	return 0;
}

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