#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<iostream>
#define inf  999999999
#define maxn 20005
using namespace std;

int g[maxn][maxn];
int dist[maxn];
int vis[maxn];
int n,m;

void dijkstra(int st){
	int i,j,mindis,u;
	memset(vis,0,sizeof(vis));
	for(i=1;i<=n;i++){
		dist[i]=g[st][i];
	}
	vis[st]=1;
	for(i=1;i<=n;i++){
		mindis=inf;
		u=-1;
		for(j=1;j<=n;j++){
			if(!vis[j]&&mindis>dist[j]){
				mindis=dist[j];
				u=j;
			}
		}
		if(u==-1)break;
		vis[u]=1;
		for(j=1;j<=n;j++){
			if(!vis[j]&&dist[j]>dist[u]+g[u][j]){
				dist[j]=dist[u]+g[u][j];
			}
		}
	}
}
int main(){
	int i,j,t;
	while(scanf("%d%d",&n,&m)!=EOF){
		for(i=1;i<=n;i++){
			for(j=1;j<=n;j++){
				if(i==j)g[i][j]=0;
				else g[i][j]=inf;
			}
			dist[i]=inf;
		}
		for(i=0;i<m;i++){
			int a,b,x;
			scanf("%d%d%d",&a,&b,&x);
			a++;b++;
			if(g[a][b]>x)g[a][b]=g[b][a]=x;
		}
		
		int u,v;
		scanf("%d%d",&u,&v);
		u++;v++;
		dijkstra(u);
		if(dist[v]==inf)printf("-1\n");
		else printf("%d\n",dist[v]);
	}
	return 0;
}
/*

3 3
0 1 1
0 2 3
1 2 1
0 2
3 1
0 1 1
1 2

*/
/*

2
-1

*/