#include<iostream>  
#include<cstdio>  
#include<cstring>  
#include<algorithm>  
using namespace std;
int pre[10010];
struct Edge
{

    int u,v,w;
} edge[10010];
bool cmp(Edge n1,Edge n2)
{
   return n1.w<n2.w;
}
int find(int root)
{ 
   return root == pre[root] ? root : pre[root] = find(pre[root]); 
}
int unionroot(int x,int y)
{
	int root1=find(x);
	int root2=find(y);
	if(root1==root2)
	return 0;
	pre[root1]=root2;
	return 1;
}
int main()
{
    int n,m,i,j,tmp,x,y,ans;
    while(scanf("%d %d",&n,&m)!=EOF)
    {
    	tmp=0;
    	ans=0;
        for(i=0;i<=10010;i++)
        pre[i]=i;
        for(i=0;i<m;i++)
        scanf("%d %d %d",&edge[i].u,&edge[i].v,&edge[i].w);
        
        sort(edge,edge+m,cmp);
        for(i=0;i<m;i++)
        {
        	x=find(edge[i].u);
        	y=find(edge[i].v);
        	if(unionroot(x,y))
        	{
        		ans+=edge[i].w;
        		tmp++;
        	}     	
        }
        if(tmp!=n-1)
        printf("impossible\n");
        else
        printf("%d\n",ans); 
		printf("\n");      	
    }
}