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 <vector>
#include <algorithm>
#include <set>
#include <queue>
#include <stack>
#include <string>
#include <map>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>

#define rep(i, n) for(int i = 0; i < n; i ++)
#define COUNT(i, n) for(int i = 1; i <= n; i ++)
#define ALL(T) T.begin(), T.end()
#define mp make_pair
#define pb push_back
#define ITER(c) __typeof((c).begin())
#define each(c, it) for(ITER(c) it = (c).begin(); it != (c).end(); it++)
#define C first
#define S second.first
#define Z second.second

using namespace std;

typedef pair<int, int> pii;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef vector<string> vs;

const int INF = 1 << 24;
const int N = 100;

int n;
bool ok[N][N];
int c[N][N];

bool check();

int main(void){
    for(int m, res; cin >> n >> m, n; cout << res << endl){
        res = 0;

        vector< pair<int, pii> > in;
        while(m--){
            int a, b, cost; cin >> a >> b >> cost;

            ok[a][b] = ok[b][a] = true;
            c[a][b] = cost;
            c[b][a] = cost;
            in.pb(mp(cost, mp(a, b)));
        }
        sort(ALL(in), greater< pair<int, pii> >());

        rep(i, in.size()){
            int a = in[i].S, b = in[i].Z;
            ok[a][b] = false;
            ok[b][a] = false;

            if(!check()){
                ok[a][b] = true;
                ok[b][a] = true;
            }
        }

        rep(i, n) for(int j = i + 1; j < n; j++) if(ok[i][j]) res += c[i][j];
    }

    return 0;
}

bool check(){
    vector<bool> used(n);
    
    queue<int> q;
    q.push(0);

    while(!q.empty()){
        int cur = q.front(); q.pop();
        if(used[cur]) continue;
        used[cur] = true;

        rep(next, n) if(ok[cur][next]) q.push(next);
    }

    return !count(ALL(used), false);
}

C++: #include <cstdio>
#include <vector>
#include <algorithm>
#include <string>
#include <map>
#include <set>
#include <queue>

using namespace std;

#define reep(i,f,t) for(int i=f ; i<int(t) ; ++i)
#define rep(i,n) reep(i, 0, n) 

typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int,int> pii;

struct Edge
{
	int src, dst;
	int weight;
	Edge(int src, int dst, int weight) : src(src), dst(dst), weight(weight) {}

	bool operator< (const Edge& e)const
	{
		return weight != e.weight ? weight > e.weight :
			src != e.src ? src < e.src : dst < e.dst;
	}
};

typedef vector<Edge> Edges;
typedef vector<Edges> Graph;

struct UnionFind
{
	vi data;

	UnionFind(int size) : data(size, -1) {}

	// xツづツづ個集ツ債づーツ閉ケツ債つキツづゥ
	bool unionSet(int x, int y)
	{
		x = root(x);
		y = root(y);
		if(x != y){
			if(data[y] < data[x])
				swap(x, y);
			data[x] += data[y];
			data[y] = x;
		}
		return x != y;
	}

	// xツづツづ個集ツ債つェツ督卍つオツつ「ツつゥツ偲ヲツ督セツつキツづゥ
	bool findSet(int x, int y)
	{
		return root(x) == root(y);
	}

	int root(int x)
	{
		return data[x] < 0 ? x : data[x] = root(data[x]);
	}
	int size(int x)
	{
		return -data[root(x)];
	}
};

pair<int, Edges> Kruskal(const Graph& g)
{
	int n = g.size();
	UnionFind uf(n);
	priority_queue<Edge> Q;

	rep(i, n) rep(j, g[i].size())
		if(i < g[i][j].dst)
			Q.push(g[i][j]);

	int total = 0;
	Edges F;
	while(F.size() < n-1 && !Q.empty()){
		Edge e = Q.top();
		Q.pop();
		printf("%d %d %d\n", e.src, e.dst, e.weight);
		if(uf.unionSet(e.src, e.dst)){
			F.push_back(e);
			total += e.weight;
		}
	}
	return pair<int, Edges>(total, F);
}

int main()
{
	int n, m;
	while(scanf("%d%d", &n, &m), n){
		Graph g(n);
		rep(i, m){
			int a, b, cost;
			scanf("%d%d%d", &a, &b, &cost);
			g[a].push_back(Edge(a, b, cost));
			g[b].push_back(Edge(b, a, cost));
		}

		pair<int, Edges> result = Kruskal(g);
		printf("%d\n", result.first);
	}
	return 0;
}

C++: #include <iostream>
#include <vector>
using namespace std;

static const int INF = 99999999;

void solve()
{
	int n, m;
	while(cin >> n >> m, n || m)
	{
		vector< vector<int> > Vec(n, vector<int>(n));
		int from, to, cost;
		for(int i = 0; i < n; ++i)
		{
			for(int j = 0; j < n; ++j)
			{
				Vec[i][j] = INF;
			}
		}
		for(int i = 0; i < m; ++i)
		{
			cin >> from >> to >> cost;
			Vec[from][to] = cost;
			Vec[to][from] = cost;
		}
		vector<int> dist(n);
		vector<bool> use(n);
		for(int i = 0; i < n; ++i)
		{
			dist[i] = INF;
			use[i] = false;
		}
		dist[0] = 0;
		int res = 0;
		while(true)
		{
			int v = -1;
			for(int i = 0; i < n; ++i)
			{
				if(!use[i] && (v == -1 || dist[i] < dist[v]))
				{
					v = i;
				}
			}
			if(v == -1)
			{
				break;
			}
			use[v] = true;
			res += dist[v];
			for(int i = 0; i < n; ++i)
			{
				dist[i] = min(dist[i], Vec[v][i]);
			}
		}
		cout << res << endl;
	}
}

int main()
{
	solve();
	return(0);
}