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;
using ll = long long; using ull = unsigned long long;
#define int ll
using vb = vector<bool>; using vvb = vector<vb>;
using vi = vector<int>; using vvi = vector<vi>;
using vl = vector<ll>; using vvl = vector<vl>;
template<class T> using V = vector<T>;
template<class T> using VV = vector<V<T>>;
#define fi first
#define se second
#define maxs(x,y) (x=max(x,y))
#define mins(x,y) (x=min(x,y))
using pii = pair<int,int>; using pll = pair<ll,ll>;
#define FOR(i,a,b) for(ll i = (a); i < (ll)(b); ++i)
#define REP(i,n) FOR(i,0,n)
#define RFOR(i,a,b) for(ll i = (ll)(b)-1;i >= a;--i)
#define RREP(i,n) RFOR(i,0,n)
#define ALL(obj) (obj).begin(), (obj).end()
#define rALL(obj) (obj).rbegin(), (obj).rend()
#define eb(val) emplace_back(val)
const double PI = acos(-1), EPS = 1e-10;
const ll MOD = 1e9+7;
void cioacc(){//accelerate cin/cout
  cin.tie(0);
  ios::sync_with_stdio(false);
}
typedef int Weight;
struct Edge {  //src:辺の始点,dst:辺の終点,weight:辺の重さ
  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 : //辺は重さが重いものを"小さい"と定義する
    e.src != f.src ? e.src < f.src : e.dst < f.dst;
}
typedef vector<Edge> Edges;
typedef vector<Edges> Graph;

//引数 g:隣接リスト,r:最小全域木の始点
//戻値 total:最小全域木の重み,T:最小全域木の辺集合
pair<Weight, Edges> prim(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) );    //始め、-1とrを結ぶ辺があると考える
  while (!Q.empty()) {
    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].begin();f!=g[e.dst].end();++f) if(!visited[f->dst]) Q.push(*f);
  }
  return pair<Weight, Edges>(total, T);
}
signed main(){
  int v,e;
  while(cin >> v >> e,v){
    Graph g(v);
    REP(i,e){
      int s,t;
      int w;
      cin >> s >> t >> w;
      g[s].push_back(Edge(s,t,w));
      g[t].push_back(Edge(t,s,w));
    }
      cout << prim(g).first << endl;
  }

}

C++: #include <cstdio>
#include <cstdlib>
#include <cmath>
#include <climits>
#include <cfloat>
#include <map>
#include <utility>
#include <set>
#include <iostream>
#include <memory>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>
#include <sstream>
#include <complex>
#include <stack>
#include <queue>
#include <cstring>
#include <sstream>
#include <cassert>
using namespace std;
static const double EPS = 1e-5;
typedef long long ll;
typedef pair<int,int> PI;
#define rep(i,n) for(int i=0;i<(int)n;++i)
#define FOR(i,c) for(__typeof((c).begin())i=(c).begin();i!=(c).end();++i)
#define ALL(c) (c).begin(), (c).end()
#define MP make_pair
#define PB push_back

typedef struct{
  int to,cost;
}edge;


vector<edge> E[100];

int n,m;

int kruskal(){
  int ret=0;
  set<int> V;
  V.insert(0);
  
  while(V.size()<n){
    int minc=10000,to,from;
    FOR(siter,V){
      rep(i,E[*siter].size()){
        if(V.count(E[*siter][i].to))continue;
        if(E[*siter][i].cost<minc){
          to=E[*siter][i].to;
          minc=E[*siter][i].cost;
        }
      }
    }
    ret+=minc;
    V.insert(to);
  }
  return ret;
}
  
    


main(){
  while(cin>>n>>m,n){
    
    rep(i,n)E[i].clear();
    
    rep(i,m){
      int a,b,c;
      cin>>a>>b>>c;
      E[a].PB((edge){b,c});
      E[b].PB((edge){a,c});
    }
    
    cout<<kruskal()<<endl;
  }
}