/*

@theme:poj 2387

@declare:最短路,从N到1点

@writer:pprp

@date:2017/9/17

*/

#include <iostream>

#include <cstring>

#include <cstdio>

#include <stack>

using namespace std;

int N, T, Min;

const int maxn = ;

const int INF = 0x3f3f3f3f;

int mp[maxn][maxn];

bool vis[maxn];

int dis[maxn];

void Dijkstra(int st)

{

    for(int i =  ; i <= N; i++)

    {

        dis[i] = mp[st][i];

    }

    vis[st] = ;

    dis[st] = ;

    int rec = -;

    for(int i =  ; i <= N ; i++)//起到了循环的作用

    {

        Min = INF;

        rec = -;

        for(int j = ; j <= N; j++)

        {

            if(!vis[j] && Min > dis[j])

            {

                rec = j;

                Min = dis[j];

            }

        }

        if(rec == -)return ;

        vis[rec] = ;

        for(int j = ; j <= N; j++)

        {

            if(!vis[j] && mp[rec][j] != INF && dis[rec] + mp[rec][j] < dis[j])

                dis[j] = mp[rec][j] + dis[rec];

        }

    }

}

int main()

{

    freopen("in.txt","r",stdin);

    int x, y, v;

    cin >> T >> N;

    for(int i =  ; i < maxn; i++)

        for(int j =  ; j < maxn; j++)

            mp[i][j] = INF;

    memset(vis,,sizeof(vis));

    for(int i =  ; i < T ; i++)

    {

        cin >> x >> y >> v;

        if(v < mp[x][y])//去重

        mp[x][y] = mp[y][x] = v;

    }

    Dijkstra();

    cout << dis[N] << endl;

    return ;

}