#include <iostream>
#include <cstring>
#include <vector>
#include <queue>

using namespace std;


//Dijkstra求最短路 II
//https://www.acwing.com/problem/content/852/

typedef pair<int,int> PII;
const int N=3e5+10,INF=0x3f3f3f3f;
vector<pair<int,int>>g[N];
int dis[N],vis[N];

void add(int a,int b,int c){
    g[a].push_back({b,c});
    g[b].push_back({a,c});
}

void dijkstra(){
    memset(dis,0x3f,sizeof dis);
    dis[1]=0;
    priority_queue<PII,vector<PII>,greater<PII>> heap;
    heap.push({0,1});       //路径长度和节点

    while(heap.size()){
        PII t=heap.top();           //找到距离最小的点
        heap.pop();
        int v=t.second,d=t.first;   //起点到v的距离
        if(!vis[v]){                //没加入最短路的点
            vis[v]=1;
            for(auto [x,w]:g[v]){      //更新距离
                if(dis[x]>d+w){
                    dis[x]=d+w;
                    heap.push({dis[x],x});
                }
            }
        }   
    }
}

int main(){
    int n,m;
    cin>>n>>m;
    while(m--){
        int a,b,c;
        cin>>a>>b>>c;
        add(a,b,c);
    }

    dijkstra();
    cout<<dis[n]<<endl;

    return 0;
}