#include<stdio.h>

 #define MAXN 1005

 #include<iostream>

 #include<algorithm>

 #define inf 10000000

 using namespace std;

 int _m[MAXN][MAXN];

 int low_cost[MAXN];

 int pre[MAXN];

 unsigned prime(int n);

 int DFS(int i,int sum,int p);

 bool mark[MAXN];

 int main()

 {

     //freopen("acm.acm","r",stdin);

     int p;

     int edge;

     unsigned tem;

     int i;

     int j;

     int u;

     int v;

     while(cin>>p>>edge)

     {

         memset(mark,false,sizeof(mark));

         for(i = ; i < p; ++ i)

         {

             for(j = ; j < p; ++ j)

                 _m[i][j] = inf;

         }

         for(i = ; i < edge; ++ i)

         {

             cin>>u>>v;

             -- u;

             -- v;

             cin>>tem;

             if(_m[u][v] == inf)

             {

                 _m[u][v] = tem;

                 _m[u][v] *= -;

                 _m[v][u] = _m[u][v];

             }

             else

                 if(tem > _m[u][v]*(-))

                 {

                     _m[u][v] = tem;

                     _m[u][v] *= -;

                     _m[v][u] = _m[u][v];

                 }

         }

         mark[] = true;

         tem = -prime(p);

         if(DFS(,,p) == p)

             cout<<tem<<endl;

         else

             cout<<-<<endl;

     }

 }

 int DFS(int i,int sum,int n)

 {

     int j;

     for(j = ; j < n; ++ j)

     {

         if(i != j && _m[i][j] != inf && !mark[j])

         {

             mark[j] = true;

             sum = DFS(j,sum+,n);

         }

     }

     return sum;

 }

 unsigned prime(int n)

 {

     int i;

     int j;

     int k;

     unsigned sum = ;

     int min;

     for(i = ; i < n; ++ i)

     {

         low_cost[i] = _m[][i];

         pre[i] = ;

     }

     for(i = ; i < n; ++ i)

     {

         min = inf;

         for(j = ; j < n; ++ j)

         {

             if(low_cost[j]&&low_cost[j] < min)

             {

                 k = j;

                 min = low_cost[j];

             }

         }

         sum += low_cost[k];

         low_cost[k] = ;

         for(j = ; j < n; ++ j)

         {

             if(_m[k][j] < low_cost[j] && low_cost[j])

             {

                 low_cost[j] = _m[k][j];

                 pre[j] = k;

             }

         }

     }

     return sum;

 }