#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
#define MAXN 210
#define INF 0x3f3f3f3f
//AC
int n,m;
struct Edge 
{
        int np,val,c;
        Edge *next,*neg;
}E[MAXN*MAXN],*V[MAXN*2];
int tope,sour=0,sink=1;
void add_edge(int x,int y,int z,int c)
{
        //cout<<"Add"<<x<<" "<<y<<" "<<z<<" "<<c<<endl;
        E[++tope].np=y;
        E[tope].val=z;
        E[tope].c=c;
        E[tope].next=V[x];
        V[x]=&E[tope];
        E[++tope].np=x;
        E[tope].val=0;
        E[tope].c=-c;
        E[tope].next=V[y];
        V[y]=&E[tope];

        E[tope].neg=&E[tope-1];
        E[tope-1].neg=&E[tope];
}
int q[MAXN*10],vis[MAXN],dis[MAXN],dfn=0;
int prev[MAXN];
Edge *path[MAXN];
int spfa()
{
        int ope=-1,clo=0,now;
        Edge *ne;
        memset(dis,INF,sizeof(dis));
        dfn++;
        q[0]=sour;
        vis[sour]=dfn;
        dis[sour]=0;
        while (ope<clo)
        {
                now=q[++ope];
                vis[now]=0;
                for (ne=V[now];ne;ne=ne->next)
                {
                        if (ne->val&&dis[ne->np]>dis[now]+ne->c)
                        {
                                dis[ne->np]=dis[now]+ne->c;
                                prev[ne->np]=now;
                                path[ne->np]=ne;
                                if (vis[ne->np]!=dfn)
                                {
                                        vis[ne->np]=dfn;
                                        q[++clo]=ne->np;
                                }
                        }
                }
        }
        return dis[sink];
}
pair<int,int> max_cost_flow()
{
        int ds,fl,now,x;
        pair<int,int> ret;
        ret.first=ret.second=0;
        while (ds=spfa(),ds!=INF)
        {
                x=sink;
                fl=INF;
                while (x!=sour)
                {
                        fl=min(fl,path[x]->val);
                        x=prev[x];
                }
                x=sink;
                while (x!=sour)
                {
                        path[x]->val-=fl;
                        path[x]->neg->val+=fl;
                        x=prev[x];
                }
                ret.first+=fl;
                ret.second+=ds*fl;
        }
        return ret;
}
int main()
{
        freopen("input.txt","r",stdin);
        int i,j,k,x,y,z;
        while (~scanf("%d%d",&n,&m))
        {
                tope=-1;
                memset(V,0,sizeof(V));
                for (i=0;i<n;i++)
                {
                        add_edge(sour,2+i,1,0);
                        add_edge(2+i+n,sink,1,0);
                }
                for(i=0;i<m;i++)
                {
                        scanf("%d%d%d",&x,&y,&z);x--;y--;
                        add_edge(2+x,2+y+n,1,z);
                }
                pair<int,int> p1;
                p1=max_cost_flow();
                if (p1.first!=n)
                {
                        printf("-1\n");
                }else
                {
                        printf("%d\n",p1.second);
                }
        }
}