#include <iostream>

#include <cstdio>

#include <cstring>

#include <queue>

using namespace std;

#define SZ 4005

#define INF 1e9+10

int head[SZ],nxt[SZ],tot = ;

struct edge

{

    int t,d;

}l[SZ];

void build(int f,int t,int d)

{

    l[++tot] = (edge){t,d};

    nxt[tot] = head[f];

    head[f] = tot;

}

queue<int> q;

bool use[SZ];

int dist[SZ];

int spfa(int s, int e)

{

    memset(dist, , sizeof(dist));

    memset(use, , sizeof(use));

    use[s] = ;

    dist[s] = ;

    q.push(s);

    while(!q.empty())

    {

        int u = q.front(); q.pop();

        use[u] = ;

        for(int i = head[u];i;i = nxt[i])

        {

            int v = l[i].t;

            if(dist[v] > dist[u] + l[i].d)

            {

                dist[v] = dist[u] + l[i].d;

                if(!use[v])

                    use[v] = , q.push(v);

            }

        }

    }

    return dist[e];

}

int main()

{

    int T, N;

    while(scanf("%d %d", &T, &N) != EOF)

    {

        memset(head, , sizeof(head));

        tot = ;

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

        {

            int x, y, z;

            scanf("%d %d %d", &x, &y, &z);

            build(x, y, z);

            build(y, x, z);

        }

        printf("%d\n", spfa(N, ));

    }

    return ;

}