#include <iostream>
#include<cstdio>
#include<vector>
#include<cstring>
#include<queue>
using namespace std;
bool vis[202];
struct node
{
    int num,d;
    node(int a,int b){num=a; d=b;}
};
vector<node> s[202];
int dis[202];
int i,j,n,u,v,m;
const int inf=0x7fffffff;


void spfa()
{
    int i,j;
    for(i=0;i<n;i++)dis[i]=inf;
    memset(vis,0,sizeof(vis));
    vis[u]=1;
    dis[u]=0;
    queue<int>Q;
    Q.push(u);
    while(!Q.empty())
    {
        int p=Q.front();
        Q.pop();
        vis[p]=0;
        for(i=0;i<s[p].size();i++)
        {
            if(dis[s[p][i].num]<=dis[p]+s[p][i].d) continue;
            dis[s[p][i].num]=dis[p]+s[p][i].d;
            if(!vis[s[p][i].num])
            {
                Q.push(s[p][i].num);
                vis[s[p][i].num]=1;
            }
        }
    }
    return;
}
int main()
{
    while(~scanf("%d%d",&n,&m))
    {
        for(i=0;i<n;i++)s[i].clear();
        for(i=1;i<=m;i++)
        {
            int x,y,d;
            scanf("%d%d%d",&x,&y,&d);
            s[x].push_back(node(y,d));
            s[y].push_back(node(x,d));
        }
        scanf("%d%d",&u,&v);
        spfa();
        if(dis[v]==inf) printf("-1\n");
          else printf("%d\n",dis[v]);
    }
    return 0;
}