const INF = 0x3f3f3f3f;
const N = 100010;
const M = 200010;
let edge = new Array(M);


//并查集
let parent = new Array(N);
//找根结点+路径压缩
let find = x => {
    if (parent[x] !== x) parent[x] = find(parent[x]);
    return parent[x];
}



let kruskal = () => {

    edge.sort((a, b) => a[2] - b[2]); //按权值排序
    let res = 0,
        cnt = 0; //res生成树长度，cnt加入生成树的边数
    //访问每一条边
    for (let i = 0; i < m; i++) {
        let e = edge[i];
        let a = find(e[0]),
            b = find(e[1]);
        if (a !== b) { //ab不在一个集合中
            res += e[2];
            cnt++;
            parent[a] = b; //加入集合
        }
    }
    if (cnt < n - 1) return INF;
    else return res;
}

let n = 0,
    m = 0;

let buf = '';
process.stdin.on('readable', function () {
    let chunk = process.stdin.read();
    if (chunk) buf += chunk.toString();
});
let getInputNums = line => line.split(' ').filter(s => s !== '').map(x => parseInt(x));
let getInputStr = line => line.split(' ').filter(s => s !== '');
process.stdin.on('end', function () {
    buf.split('\n').forEach(function (line, lineIdx) {
        if (lineIdx === 0) {
            n = getInputNums(line)[0];
            m = getInputNums(line)[1];
            for (let i = 1; i <= n; i++) parent[i] = i;   //并查集初始化
        } else if (lineIdx <= m) {
            let arr = getInputNums(line);
            let a = arr[0];
            let b = arr[1];
            let w = arr[2];
            edge.push([a, b, w]);
            if (lineIdx === m) {
                let t = kruskal();
                if (t === INF) console.log('impossible');
                else console.log(t);


            }
        }
    });
});