using namespace std;
#include<cstdio>
#include<cstring>
#include<vector>
#define Nm 101
#define Mm 1000
int X[Mm],Y[Mm],Z[Mm],XX[Mm],YY[Mm],ZZ[Mm],V[Nm],A[Nm],n,m,mm,k;
vector<int> C[Nm];

void read()
{
    int i;
    
    freopen("party.in","r",stdin);
    scanf("%d%d",&n,&m);
    for(i=0;i<m;++i)
    {
        scanf("%d%d%d",X+i,Y+i,Z+i);
        C[X[i]].push_back(i);
        C[Y[i]].push_back(i);
    }
}

bool set(int x, int v)
{
    vector<int>::iterator it;

    V[x]=v;
    for(it=C[x].begin();it!=C[x].end();++it)
    {
        if(V[X[*it]] && V[Y[*it]])
            if(V[X[*it]]-1^Z[*it]&1 || V[Y[*it]]-1^Z[*it]&2)
                continue;
            else
            {
                V[x]=0;
                return 0;
            }
        else
        {
            if(X[*it]==x && !(V[x]-1^Z[*it]&1))
                if(!set(Y[*it],(1^Z[*it]&2)+1))
                {
                    V[x]=0;
                    return 0;
                }
            if(Y[*it]==x && !(V[x]-1^Z[*it]&2))
                if(!set(X[*it],(1^Z[*it]&1)+1))
                {
                    V[x]=0;
                    return 0;
                }
        }
    }
    return 1;
}

void solve()
{
    int i;

    while(m)
    {
        if(!set(X[0],1))
            set(X[0],2);
        for(i=1;i<=n;++i)
            C[i].clear();
        for(mm=i=0;i<m;++i)
            if(!V[X[i]] && !V[Y[i]])
            {
                XX[mm]=X[i];
                YY[mm]=Y[i];
                ZZ[mm++]=Z[i];
            }
        m=mm;
        memcpy(X,XX,Mm*sizeof(int));
        memcpy(Y,YY,Mm*sizeof(int));
        memcpy(Z,ZZ,Mm*sizeof(int));
        for(i=0;i<m;++i)
        {
            C[X[i]].push_back(i);
            C[Y[i]].push_back(i);
        }
    }

    for(i=1;i<=n;++i)
        if(V[i]==2)
            A[k++]=i;
}

void write()
{
    int i;

    freopen("party.out","w",stdout);
    printf("%d\n",k);
    for(i=0;i<k;++i)
        printf("%d\n",A[i]);
}

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