#include <stdio.h>
#include <string.h>
#define MAX 210
#define INF 100000000
int dp[MAX][MAX] ;

void floyd(int n)
{
	for(int k = 0 ; k < n ; ++k)
	{
		for(int i = 0 ; i < n ; ++i)
		{
			if(dp[i][k] == INF)
			{
				continue ;
			}
			for(int j = 0 ; j < n ; ++j)
			{
				if(dp[i][j]>dp[i][k]+dp[k][j])
				{
					dp[i][j] = dp[i][k]+dp[k][j] ;
				}
			}
		}
	}
}

int main()
{
	int n , m ;
	while(~scanf("%d%d",&n,&m))
	{
		for(int i = 0 ; i <= n ; ++i)
		{
			for(int j = 0 ; j <= i ; ++j)
			{
				dp[i][j]=dp[j][i] = INF ;
			}
			dp[i][i] = 0 ;
		}
		for(int i = 0 ; i < m ; ++i)
		{
			int a , b , x ;
			scanf("%d%d%d",&a,&b,&x);
			if(dp[a][b] > x)		//千万别忘了判重 
				dp[a][b] = dp[b][a] = x ;
		}
		floyd(n);
		int x, y ;
		scanf("%d%d",&x,&y);
		if(dp[x][y] == INF)
		{
			puts("-1") ;
		}
		else
		{
			printf("%d\n",dp[x][y]);
		}
	}
	return 0 ;
}

#include <stdio.h>
#include <string.h>
#define MAX 210
#define INF 100000000
int graph[MAX][MAX] , dis[MAX];

void Bellman_Ford(int u , int n)
{
	for(int i = 0 ; i < n ; ++i)
	{
		dis[i] = INF ;
	}
	dis[u] = 0 ;
	for(int k = 0 ; k < n-1 ; ++k)
	{
		for(int i = 0 ; i < n ; ++i)
		{
			for(int j = 0 ; j < n ; ++j)
			{
				if(dis[i]>dis[j]+graph[j][i])
				{
					dis[i] = dis[j]+graph[j][i] ;
				}
			}
		}
	}
}

int main()
{
	int n , m ;
	while(~scanf("%d%d",&n,&m))
	{
		for(int i = 0 ; i <= n ; ++i)
		{
			for(int j = 0 ; j <= i ; ++j)
			{
				graph[i][j]=graph[j][i] = INF ;
			}
			graph[i][i] = 0 ;
		}
		for(int i = 0 ; i < m ; ++i)
		{
			int a , b , x ;
			scanf("%d%d%d",&a,&b,&x);
			if(graph[a][b] > x)		//千万别忘了判重 
				graph[a][b] = graph[b][a] = x ;
		}
		int x, y ;
		scanf("%d%d",&x,&y);
		Bellman_Ford(x,n);
		if(dis[y] == INF)
		{
			puts("-1") ;
		}
		else
		{
			printf("%d\n",dis[y]);
		}
	}
	return 0 ;
}