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<string>
#include<cmath>
#include<queue>
#include<vector>
#include<bits//stdc++.h>
#include<functional>
using namespace std;
int parent [100];
int root(int x){
	if(parent[x]==x) return x;
	return parent[x]=root(parent[x]);
}
void unite(int x,int y){
	x=root(x);
	y=root(y);
	parent[x]=y;
}
bool same(int x,int y){
	return root(x)==root(y);
}
struct P{
	int from,to,cost;
};
bool operator<(P a,P b){
	return a.cost<b.cost;
}
bool operator>(P a,P b){
	return a.cost>b.cost;
}
int main() {
	int n,m;
	while(cin>>n>>m&&n!=0&&m!=0){
	int a,b,c;
	for(int i=0;i<n;i++)parent[i]=i;
	priority_queue<P, vector<P>, greater<P>>p;
	for(int i=0;i<m;i++){
		cin>>a>>b>>c;
		p.push(P{a,b,c});
	}
	int sum=0,d=0;
	while(d!=n-1){
		P t=p.top();p.pop();
		if(!same(t.from,t.to)){
			unite(t.from,t.to);
			d++;
			sum+=t.cost;
		}
	}
	cout<<sum<<endl;
}
}

C++: #include <iostream>
#include <utility>
#include <string>
#include <algorithm>
#include <set>
#include <deque>
#include <vector>
#define MAX 25000
#define rep(i,p) for(int i=0;i<p;i++)
#define rep1(i,p) for(int i=1;i<=p;i++)
#define pb push_back
using namespace std;
int n,m,sum,num;
int A[MAX];
int B[MAX];
int C[MAX];
int V[MAX];
pair<int,int> bridge[MAX];
int root (int child) {
  int a = child;
  while (V[a] != a) {
    a = V[a];
  }
  return a;
}
int main(){
  while (1) {
    cin >> n >> m;
    if (n==0 && m==0) return 0;
    // n : city
    // m : bridge
    rep(j,m) {
      cin >> A[j] >> B[j] >> C[j];
      bridge[j].first = C[j];
      bridge[j].second = j;
    }
    // sort by lenght of bridge
    sort(bridge, bridge+m);
    sum = 0;
    // Union Find Tree
    rep(i,m) V[i] = i;
    rep(i,m) {
      num = bridge[i].second;
      int ra = root(A[num]);
      int rb = root(B[num]);
      if (ra != rb) {
        V[ra] = rb;
        sum += bridge[i].first;
      }
      // cout << bridge[i].first << " " << bridge[i].second << endl;
    }
    cout << sum << endl;
  }
  return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
typedef pair<int, int> P;

int n, m;
vector<P> branch[128];

int prim();

int main()
{
    while (scanf("%d %d", &n, &m), n != 0){
        for (int i = 0; i < n; i++) branch[i].clear();

        for (int i = 0; i < m; i++){
            int a, b, c;

            scanf("%d %d %d", &a, &b, &c);
            branch[a].push_back(P(c, b));
            branch[b].push_back(P(c, a));
        }
        printf("%d\n", prim());
    }

    return 0;
}

int prim()
{
    bool v[1024];
    priority_queue<P, vector<P>, greater<P> > q;
    int sum = 0;

    q.push(P(0, 0));
    v[0] = 0;
    while (!q.empty()){
        P p = q.top(); q.pop();

        if (v[p.second]) continue;
        v[p.second] = true;
        sum += p.first;
        for (int i = 0; i < branch[p.second].size(); i++){
            q.push(branch[p.second][i]);
        }
    }

    return sum;
}

C++: #include<iostream>
#include<cstdio>
#include<algorithm>
#include<queue>
#include<cstring>
#include<cstdlib>
#include<vector>
#define MAX_V 1000
#define INF 1<<29
#define cl(a,b) for(int i=0;i<a;i++)for(int j=0;j<b;j++)cost[i][j] = INF;
#define de(a)  for(int i=0;i<a;i++){cout << mincost[i] << " "; if(i == a-1){cout << endl;}}
#define de2(a,b) for(int I=0;I<a;I++){for(int j=0;j<b;j++){cout << cost[I][j] << " ";}cout << endl;}cout << endl;
using namespace std;

int cost[MAX_V][MAX_V];
int mincost[MAX_V];
bool used[MAX_V];
int V;
 bool connect[10000];

int prime()
{
  for(int i=0;i<V;++i)
    {
      mincost[i]=INF;
      used[i]=false;
    }

  mincost[0] = 0;
  int res = 0;

  //de(10);
  

  //de2(10,10);
  

  while(true)
    {
      int v = -1; 
      for(int u = 0; u<V ; u++ )
	{
	  if(connect[u] && !used[u] && (v == -1 || mincost[u] < mincost[v]))
	    {
	      v = u;
	      //cout << "v = " << v << endl;
	    }
	}

      if(v == -1)break;
      used[v] = true;
      res += mincost[v];

      for(int u = 0; u < V; u++)
	{
	  if(!connect[u]){}
	  else{
	  mincost[u] = min(mincost[u],cost[v][u]);
	  //cout << "mincost[u] = " << mincost[u] << ", cost[v][u] = " << cost[v][u] << endl;
	  }
	}
    }
  return res;
}



int main()
{

  int n,m,a,b;
 

  while(true)
    {
      cin >> n >> m;
      if(n == 0 && m == 0)break;
      cl(m,m);
      memset(connect,false,sizeof(connect));

      V = m;
      for(int i=0;i<m;i++)
	{
	  cin >> a >> b;
	  cin >> cost[a][b];
	  cost[b][a] = cost[a][b];
	  connect[a] = true;
	  connect[b] = true;
	}
      /*     
 for(int i=0;i<m;i++)
	{
	  if(!connect[i])
	    {


	    }
	}
      */


      cout << prime() << endl;




    }

}