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++: #define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <vector>
#include <iostream>
#include <string>
#include <cstdio>
#include <algorithm>
using namespace std;
int par[104];
int ran[105];
void init(int n) {
	for (int i = 0; i<n; i++) {
		par[i] = i;
		ran[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 (ran[x]<ran[y]) {
		par[x] = y;
	}
	else {
		par[y] = x;
		if (ran[x] == ran[y]) ran[x]++;
	}
}
bool same(int x, int y) {
	return find(x) == find(y);
}
struct edge { int s, t, cost; };
bool comp(edge&e1, edge &e2) {
	return e1.cost < e2.cost;
}
int main()
{
	int n, m;
	while (cin >> n >> m, n != 0) {
		init(n);
		edge b[10008];
		int x, y, z;
		for (int i = 0; i < m; i++) {
			cin >> x >> y >> z;
			b[i].s = x;
			b[i].t = y;
			b[i].cost = z;
		}
		int ans = 0;
		sort(b, b + m, comp);
		for (int i = 0; i < m; i++) {
			edge now = b[i];
			if (!same(now.s, now.t)) {
				unite(now.s, now.t);
				ans += now.cost;
			}
		}cout << ans;
	}
	return 0;
}

C++: //
//  main.cpp
//
// g++ -std=c++14 main.cpp
//

//#include "main.hpp"
#include <iostream>
#include <vector>
#include <stack>
#include <algorithm>
#include <math.h>
#include <queue>
#include <tuple>
using namespace std;
typedef long long ll;

int par[100010];
int rnk[100010];
ll sze[100010];

// 初期化
void init(int n) {
    for (int i = 0; i < n; i++) {
        par[i] = i;
        rnk[i] = 0;
        sze[i] = 1;
    }
}

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

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

// 同じ木にあるか
bool same(int x, int y) {
    return find(x) == find(y);
}

int main(void){
    int n, m;
    while (cin >> n >> m) {
        if (n == m && m == 0) return 0;
        
        vector<tuple<int, int, int> > br;
        for (int i = 0; i < m; i++) {
            int a, b, c;
            cin >> a >> b >> c;
            br.emplace_back(c, a, b);
        }
        
        sort(br.begin(), br.end());
        
        init(n);
        int ans = 0;
        for (int i = 0; i < br.size(); i++) {
            if (!same(get<1>(br[i]), get<2>(br[i]))) {
                unite(get<1>(br[i]), get<2>(br[i]));
                ans += get<0>(br[i]);
            }
        }
        
        cout << ans << endl;
    }
}

C++: #include "bits/stdc++.h"
using namespace std;

typedef long long lli;
typedef pair<int,int> pii;
#define rep(i,n) for(lli i=0;i<(lli)(n);i++)
#define all(a)  (a).begin(),(a).end()
#define pb push_back
#define INF 999999999

int pass[200][200];


int main(){
    int n,m;
    while(cin>>n>>m){
        if(n==0&&m==0)break;
        
        rep(i,200)rep(j,200)pass[i][j]=INF;
        
        rep(i,m){
            int a,b,c;
            cin>>a>>b>>c;
            pass[a][b]=c;
            pass[b][a]=c;
        }
        
        bool used[200];
        int mincost[200];
        rep(i,200)mincost[i]=INF;
        rep(i,200)used[i]=false;
        
        int res=0;
        mincost[0]=0;

        while(1){
            int v=-1;
            rep(i,n){
                if( !used[i]&&(v==-1||mincost[v]>mincost[i]) )v=i;
            }
            
            if(v==-1)break;
            
            used[v]=true;
            res+=mincost[v];
            
            rep(i,n){
                mincost[i] = min( mincost[i] , pass[v][i] );
            }
        }
        cout<<res<<endl;
    }
}