#include <cstdio>
using namespace std;

int ystojh[5001],jhst[5001],jhen[5001],ysnext[5001],jhysnum[5001];
bool used[5001],map[5001][5001];

void combineit(int jha,int jhb)
{
	int pos;
	jhysnum[jha]=jhysnum[jha]+jhysnum[jhb];
	ysnext[jhen[jha]]=jhst[jhb];
	pos=jhst[jhb];
	while (pos)
	{
		ystojh[pos]=jha;
		pos=ysnext[pos];
	}
	jhen[jha]=jhen[jhb];
}

void combine(int jha,int jhb)
{
	if (jha==jhb)
		return;
	if (jhysnum[jha]>=jhysnum[jhb])
		combineit(jha,jhb);
	else
		combineit(jhb,jha);
}

int main(void)
{
	freopen("classroom.in","r",stdin);
	freopen("classroom.out","w",stdout);
	int i,j,k,n,m,x,y,type,maxnum,maxjh,temp;
	scanf("%d%d",&n,&m);
	for (i=1;i<=n;i++)
	{
		ystojh[i]=i;
		jhst[i]=i;
		jhen[i]=i;
		jhysnum[i]=1;
	}
	for (i=1;i<=m;i++)
	{
		scanf("%d%d%d",&x,&y,&type);
		if (type==1)
			map[x][y]=true;
		else
		{
			map[x][y]=true;
			map[y][x]=true;
		}
	}
	for (k=1;k<=n;k++)
		for (i=1;i<=n;i++)
			if (k!=i)
				for (j=1;j<=n;j++)
					if (i!=j&&k!=j)
						if (map[i][k]&&map[k][j])
							map[i][j]=true;
	for (i=1;i<=n;i++)
		for (j=1;j<=n;j++)
			if (i!=j)
				if (map[i][j]&&map[j][i])
					combine(ystojh[i],ystojh[j]);
	maxnum=0;
	for (i=1;i<=n;i++)
	{
		temp=ystojh[i];
		if (!used[temp]&&maxnum<jhysnum[temp])
		{
			maxnum=jhysnum[temp];
			maxjh=temp;
			used[temp]=true;
		}
	}
	printf("%d\n",maxnum);
	x=0;
	for (i=1;i<=n;i++)
		if (ystojh[i]==maxjh)
		{
			if (x)
				printf(" ");
			else
				x=1;
			printf("%d",i);
		}
	printf("\n");
	return(0);
}