#include<cstdio>
#include<iostream>
#include<cstring>
#include<algorithm>

using namespace std;

const int N = 100000;
const int inf = 0x7fffffff;

struct node{
    int a;
    int b;
    int val;
    bool operator < (const node &x) const
    {
        return x.val>val;
    } 
}e[N << 1];

int n,m,fa[N << 1];

int find(int x)
{
    return fa[x] == x ? x : fa[x] = find(fa[x]);
}

int read()
{
    char c = getchar();
    int f = 1, x = 0;
    while(!isdigit(c)) {if(c == '-') f = -1;c = getchar();}
    while(isdigit(c)){x = x * 10 + c - 48;c = getchar();}
    return x * f;
}

int ans,cnt;

void kru()
{
    sort(e+1,e+m+1);
    for(int i=1;i<=m;i++)
    {
        int x,y;
        x = find(e[i].a);
        y = find(e[i].b);
        if(x == y) continue;
        fa[x]=y;
        ans+=e[i].val;
        cnt++;
        if(cnt>=n-1) break;
    }
    if(cnt<n-1)
    {
        puts("impossible"); 
        exit(0);
    }
}
int main()
{
    n = read(),m = read();
    for(int i=1;i<=m;i++)
    {
        e[i].a = read();
        e[i].b = read();
        e[i].val = read();
    }
    for(int i=1;i<=n;i++) fa[i]=i;
    kru();
    printf("%d",ans);
}