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 <iostream>
#include <algorithm>
using namespace std;

#define MAX_N 100

int par[MAX_N];
int rank[MAX_N];

#define MAX_E 100
struct edge { int u, v, cost; };
edge es[MAX_E];

int V, E;

void init_union_find(int n) {
  for(int i=0; i<n; i++) {
    par[i] = i;
    rank[i] = 0;
  }
}

int find(int x) {
  if(par[x] == x) {
    return x;
  } else {
    return par[x] = find(par[x]);
  }
}

void unite(int x, int y) {
  x = find(x);
  y = find(y);
  if(x == y) return;
  
  if(rank[x] < rank[y]) {
    par[x] = y;
  } else {
    par[y] = x;
    if(rank[x] == rank[y]) rank[x] ++;
  }
}

bool same(int x, int y) {
  return find(x) == find(y);
}

bool comp(const edge& e1, const edge& e2) {
  return e1.cost < e2.cost;
}

int kruskal() {
  sort(es, es + E, comp);
  init_union_find(V);
  int res = 0;
  for(int i=0; i<E; i++) {
    edge e = es[i];
    if(!same(e.u, e.v)) {
      unite(e.u, e.v);
      res += e.cost;
    }
  }
  return res;
}

int main() {

  while(cin >> V >> E && (V||E)) {
    E *= 2;
    for(int i=0; i<E; i+=2) {
      int a, b, c;
      cin >> a >> b >> c;
      es[i].u = a, es[i].v = b, es[i].cost = c;
      es[i].u = b, es[i].v = a, es[i].cost = c;
    }
    cout << kruskal() << endl;
  }
  
  return 0;
}

C++: #include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <ctime>
#include <iostream>
#include <algorithm>
#include <sstream>
#include <string>
#include <vector>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <utility>
using namespace std;

#define rep(i,n) for(int (i)=0; (i)<(int)(n); ++(i))
#define foreach(c,i) for(__typeof((c).begin()) i=(c).begin();i!=(c).end();i++)

// uf
namespace uf
{
  const int Size = 1002;
  int par[Size];
  int rank[Size];
  
  void init(int n) {
    for (int i = 0; i < n; ++i) {
      par[i] = i;
      rank[i] = 0;
    }
  }
    
  int find(int x) {
    if (par[x] == x) return x;
    return par[x] = find(par[x]);
  }
  
  void unite(int x, int y) {
    x = find(x);
    y = find(y);
    if (x == y) return;
    
    if (rank[x] < rank[y]) {
      par[x] = y;
    } else {
      par[y] = x;
      if (rank[x] == rank[y]) rank[x]++;
    }
  }
  
  bool same(int x, int y) {
    return find(x) == find(y);
  }
}; /* uf */ 

// mst
struct edge {
  int u, v, cost;
};

bool comp(const edge& a, const edge& b) {
  return a.cost < b.cost;
}

const int MAX_E = 10002;
edge es[MAX_E];
int V, E;

int kruskal() {
  sort(es, es + E, comp);
  uf::init(V);
  int res = 0;
  for (int i = 0; i < V; ++i) {
    edge e = es[i];
    if (!uf::same(e.u, e.v)) {
      uf::unite(e.u, e.v);
      res += e.cost;
    }
  }
  return res;
}

int solve() {
  int a, b, cost;
  rep (i,E) {
    cin >> a >> b >> cost;
    es[i] = (edge){ a, b, cost };
  }
  return kruskal();
}

int main() {
  while (cin >> V >> E, V|E) {
    cout << solve() << endl;
  }
  return 0;
}

C++: #include<iostream>
#include<cstring>
#include<vector>
#include<queue>
using namespace std;
int main()
{
  int n,m;
  for(;cin>>n>>m,n;)
    {
      int edge[n][n];
      memset(edge,-1,sizeof(edge));
      for(int i=0;i<m;i++)
	{
	  int a,b,cost;
	  cin>>a>>b>>cost;
	  edge[a][b]=cost;
	  edge[b][a]=cost;
	}
      bool closed[n];
      int cnt=n-1;
      int ans=0;
      memset(closed,false,sizeof(closed));
      closed[0]=true;
      priority_queue<pair<int,int>, vector<pair<int,int> > ,greater<pair<int,int> > > qu;
      for(int i=0;i<m;i++)
	{
	  if(edge[0][i]!=-1)
	    qu.push(make_pair(i,edge[0][i]));
	}
      while(true)
	{
	  int pos=qu.top().first;
	  int cost=qu.top().second;
	  qu.pop();
	  if(closed[pos])
	    continue;
	  closed[pos]=true;
	  ans+=cost;
	  cnt--;
	  if(cnt<=0)
	    break;
	  for(int i=0;i<m;i++)
	    {
	      if(!closed[i]&&edge[pos][i]!=-1)
		qu.push(make_pair(i,edge[pos][i]));
	    }
	}
      cout<<ans<<endl;
    }

}

C++: 
// O(n'2 + e)
// テ」ツδ療」ツδェテ」ツδ?ヲツウツ?

#include <iostream>
#include <algorithm>
#define MAX 100
#define INF 999999

using namespace std;

int cost[MAX + 1][MAX + 1];
int mincost[MAX + 1];
bool used[MAX + 1];

int prim(int V){ // テ」ツδ偲」ツδシテ」ツδ嘉ヲツ閉ー

  for(int i = 0 ; i < V ; i++){ // テ・ツ按敕ヲツ慊淌・ツ個?
    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;
      // テ、ツスツソテ」ツ?」テ」ツ?ヲテ」ツ?ェテ」ツ??」ツつ?」ツ?、テ」ツ?ァテヲツ慊?」ツつづ・ツーツ湘」ツ?陛」ツ??ostテ」ツ?ョテヲツキツサテ・ツュツ療」ツつ津ヲツ篠「テ」ツ??
    }
    if(v == -1) break;
    used[v] = true; // テ」ツ?凖」ツ?ァテ」ツ?ォテ、ツスツソテ」ツ?」テ」ツ?淌」ツ?禿」ツ?ィテ」ツ?ォテ」ツ?凖」ツつ?
    res += mincost[v];

    for(int u = 0 ; u < V ; u++){
      mincost[u] = min(mincost[u], cost[v][u]);
      // mincostテ」ツ?ョテァツ「ツコテ・ツョツ?
    }
  }
  return res;
}

int main(void){

  int n, m;
  while(cin >> n >> m, n + m){

    fill(cost[0], cost[MAX], INF);

    for(int i = 0 ; i < m ; i++){
      int a, b, c;
      cin >> a >> b >> c;
      cost[a][b] = cost[b][a] = c;
    }
    cout << prim(n) << endl;
  }
  return 0;
}