#include<iostream>
#include<algorithm>
using namespace std;
const long long N=2e5+5;
struct node{
    long long u,v,w,used,z;
}edge[N];
bool cmp(node x,node y){
    return x.w<y.w;
}
long long n,m,fa[N],Fa[N],tot1,tot2,p[N],l=1,r;
long long finded(long long x){
    if(fa[x]!=x)fa[x]=finded(fa[x]);
    return fa[x];
}
long long Finded(long long x){
    if(Fa[x]!=x)Fa[x]=Finded(Fa[x]);
    return Fa[x];
}
int main(){
    cin>>n>>m;
    for(long long i=1;i<=n;++i){
        fa[i]=i;Fa[i]=i;
    }
    for(long long i=1;i<=m;++i){
        cin>>edge[i].u>>edge[i].v>>edge[i].w;
        edge[i].used=0;
    }
    sort(edge+1,edge+m+1,cmp);
    long long cnt=n-1,now=0;
    while(cnt){
        now++;
        long long u=edge[now].u,v=edge[now].v,w=edge[now].w;
        if(Finded(u)!=Finded(v)){
            Fa[Finded(u)]=Finded(v);
            tot1+=w;
            cnt--;
            edge[now].used=1;
        }
    }
//    cout<<tot1;
    cnt=n-1,now=0;
    while(cnt){
        now++;
        if(now==m+1){
            cout<<"-1";
            return 0;
        }
        if(edge[now].used){
            p[++r]=now;
            continue;
        }
        long long u=edge[now].u,v=edge[now].v,w=edge[now].w;
        if(finded(u)!=finded(v)){
            fa[finded(u)]=finded(v);
            tot2+=w;
            cnt--;
            for(long long i=l;i<=r;++i){
                if(finded(edge[p[i]].u)==finded(edge[p[i]].v)){
                    edge[p[i]].z=w+1;
                    swap(p[l],p[i]);
                    ++l;
                }
            }
        }
    }
    long long ans=0;
    for(long long i=1;i<=m;++i){
        if(edge[i].used)ans+=edge[i].z;
    }
    cout<<ans-tot1;
    return 0;
}