const INF = 0x3f3f3f3f;
const N = 510;

let res = 0;
let graph = [];
for (let i = 0; i < N; i++) graph[i] = new Array(N).fill(INF);
let dist = new Array(N).fill(INF);
let st = new Int32Array(N);

let prim = () => {
    for (let i = 0; i < n; i++) {
        let t = -1;
        for (let j = 1; j <= n; j++) {
            if (!st[j] && (t === -1 || dist[t] > dist[j])) t = j;
        }
        if (i && dist[t] === INF) return false;
        if (i) res += dist[t];
        st[t]++;
        for (let j = 1; j <= n; j++)
            dist[j] = Math.min(dist[j], graph[j][t]);
    }
    return true;

}

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];
        } else if (lineIdx <= m) {
            let arr = getInputNums(line);
            let a = arr[0];
            let b = arr[1];
            let c = arr[2];
            if (a !== b) graph[a][b] = graph[b][a] = Math.min(graph[a][b], c); //最小生成树中无环   无向图
            if (lineIdx === m) {
                let s = prim();
                if (s) console.log(res);
                else console.log('impossible');
            }
        }
    });
});