Go: // Find the minimum spanning tree by the Kruskal algorithm
// -------------------------------------------------------
// Kruskal(G):
//     A = ∅
//     foreach v ∈ G.V:
//        MAKE-SET(v)
//     foreach (u, v) in G.E ordered by weight(u, v), increasing:
//         if FIND-SET(u) ≠ FIND-SET(v):
//             A = A ∪ {(u, v)}
//             UNION(u, v)
//     return A
//
// Ref: https://en.wikipedia.org/wiki/Kruskal%27s_algorithm

package main

import (
	"bufio"
	"os"
	"sort"
	"strconv"
	"strings"
	"fmt"
	)

var scanner = bufio.NewScanner(os.Stdin)
var (
	matrix [][]int
)

type Edge struct {
	a, b, cost, added int
}
type ByCost []Edge

var edges ByCost

func (a ByCost) Len() int           { return len(a) }
func (a ByCost) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
func (a ByCost) Less(i, j int) bool { return a[i].cost < a[j].cost }

func main() {
	for scanner.Scan() {
		buf := strings.Split(scanner.Text(), " ")
		n, _ := strconv.Atoi(buf[0])
		m, _ := strconv.Atoi(buf[1])
		if n == 0 && m == 0 {
			break
		}
		matrix = make([][]int, n)
		for i := range matrix {
			matrix[i] = make([]int, n)
		}
		for i := 0; i < m; i++ {
			scanner.Scan()
			buf_ := strings.Split(scanner.Text(), " ")
			a, _ := strconv.Atoi(buf_[0])
			b, _ := strconv.Atoi(buf_[1])
			cost, _ := strconv.Atoi(buf_[2])
			matrix[a][b] = cost
			matrix[b][a] = cost
		}
		sum := Kruskal(n)
		fmt.Println(sum)
		if len(edges) > 0 {
			edges = []Edge{}
		}
	}
}

func Kruskal_func(size, edge_num int) int {
	for i := 0; i < size; i++ {
		for j := 0; j < size; j++ {
			if matrix[i][j] > 0 {
				tmp := Edge{i, j, matrix[i][j], 0}
				edges = append(edges, tmp)
			}
		}
	}
	sort.Sort(ByCost(edges))
	UF_Init(edge_num)
	for i := 0; i < edge_num; i++ {
		a := edges[i].a
		b := edges[i].b
		if UF_Find(a) != UF_Find(b) {
			edges[i].added = 1
			UF_Union(UF_Find(a), UF_Find(b))
		}
	}
	sum := 0
	for i := 0; i < edge_num; i++ {
		if edges[i].added != 0 {
			// log.Printf("edge(%d,%d) is added\n", edges[i].a, edges[i].b)
			sum += edges[i].cost
		}
	}
	return sum
}

func Kruskal(size int) int {
	edge_num := 0
	for i := 0; i < size; i++ {
		for j := 0; j < size; j++ {
			if matrix[i][j] > 0 {
				edge_num++
			}
		}
	}
	return Kruskal_func(size, edge_num)
}

/*** Union-Find functions ***/
var UF_Parent []int
var UF_Rank []int

func UF_Init(n int) {
	UF_Parent = make([]int, n)
	UF_Rank = make([]int, n)
	for i := 0; i < n; i++ {
		UF_Parent[i] = i
		UF_Rank[i] = 0
	}
}
func UF_Union(a, b int) {
	if UF_Rank[a] < UF_Rank[b] {
		UF_Parent[a] = b
	} else {
		UF_Parent[b] = a
	}
	if UF_Rank[a] == UF_Rank[b] {
		UF_Rank[a]++
	}
}
func UF_Find(a int) int {
	if UF_Parent[a] == a {
		return a
	}
	return UF_Find(UF_Parent[a])
}
/*** Union-Find functions ***/

C++: #include <bits/stdc++.h>

using namespace std;

#define MAX_V 114
#define INF 1e9

int cost[MAX_V][MAX_V];
int mincost[MAX_V];
bool used[MAX_V];
int V;

int prim(){
  for(int i = 0 ; i < V ; i++){
    mincost[i] = INF;
    used[i] = false;
  }
  mincost[0] = 0;
  int res = 0;
  
  while(true){
    int v = -1;
  
    for(int u = 0 ; u < V ; u++){
      if(!used[u] && (v == -1 || mincost[u] < mincost[v])){
        v = u;
      }
    }
    if(v == -1){ break; }
    used[v] = true;        
    res += mincost[v];     

    for(int u = 0 ; u < V ; u++){
      mincost[u] = min(mincost[u],cost[v][u]);
    }
  }
  return res;
}

int main(){
  int E,s,t,w;
  while(cin >> V >> E,V){
    for(int i = 0 ; i < V ; i++){
      for(int j = 0 ; j < V ; j++){
        cost[i][j] = INF;
      }
    }
    for(int i = 0 ; i < E ; i++){
      cin >> s >> t >> w;
      cost[s][t] = cost[t][s] = w;
    }
    cout << prim() << endl;
  }
  return 0;
}

C++: #include <iostream>
#include <vector>
#include <string>
#include <sstream>
#include <cstdio>
#include <cmath>
#include <algorithm>
#include <set>
#include <queue>
using namespace std;

#define loop(i,a,b) for(int i=(a);i<int(b);i++)
#define rep(i,b) loop(i,0,b)

// テ」ツつーテ」ツδゥテ」ツδ陛ァツ板ィテ」ツδ佚」ツδε」ツδ?

typedef int Weight;
struct Edge {
    int src, dst;
    Weight weight;
    Edge(int src, int dst, Weight weight) :
        src(src), dst(dst), weight(weight) { }
};
bool operator < (const Edge &e, const Edge &f) {
    return e.weight != f.weight ? e.weight > f.weight : // !!INVERSE!!
        e.src != f.src ? e.src < f.src : e.dst < f.dst;
}
typedef vector<Edge> Edges;
typedef vector<Edges> Graph;

typedef vector<Weight> Array;
typedef vector<Array> Matrix;

// テヲツ慊?・ツーツ湘・ツ?ィテ・ツ淞淌ヲツ慊ィ(Minimum Spanning Tree) by Prim Algorithm
/*
  g : テ」ツつーテ」ツδゥテ」ツδ?
  r : テヲツ慊?・ツ按敕」ツ?ォテ・ツ青ォテ」ツつ?ゥツ?づァツつケ
*/
pair<Weight, Edges> MST(const Graph &g, int r = 0) {
    int n = g.size(); Edges T; Weight total = 0;
    vector<bool> visited(n);
    priority_queue<Edge> q;
    q.push(Edge(-1, r, 0));
    while (q.size()) {
        Edge e = q.top(); q.pop();
        if (visited[e.dst]) continue;
        T.push_back(e);
        total += e.weight;
        visited[e.dst] = true;
        for(auto& f: g[e.dst]) if (!visited[f.dst]) q.push(f);
    }
    return pair<Weight, Edges>(total, T);
}

int main(){
    int n,m;
    while(cin>>n>>m && n){
        Graph g(n);
        rep(i,m){
            int a,b,c;
            cin>>a>>b>>c;
            g[a].emplace_back(a,b,c);
            g[b].emplace_back(b,a,c);
        }
        cout << MST(g).first << endl;
    }
}