#include<stdio.h>
int p[1001],n,m,i,a,b,j,w[1001],c[1001],r,k,z,d[1001],f[1001][1001],g[1001][1001],e[1001],h[1001];
void D(int x)
{
	int i;
	c[x]=1;
	for(i=0;i<e[x];++i)
        if(!c[f[x][i]])
            D(f[x][i]);
	w[++r]=x;
}
void T(int x)
{
	c[x]=0;
	if(p[x]==2) {
		p[x]=0;
       	if(x>n)
            p[x-n]=1;
       	else
            p[x+n]=1;
	}
	int i;
	for(i=0;i<h[x];++i)
        if(c[g[x][i]])
            T(g[x][i]);
}
int main()
{
	freopen("party.in","r",stdin),freopen("party.out","w",stdout),scanf("%d%d",&n,&m);
	while(m--) {
		scanf("%d%d%d",&a,&b,&z);
       	if(!z)
            f[a+n][e[a+n]++]=b,f[b+n][e[b+n]++]=a,g[b][h[b]++]=a+n,g[a][h[a]++]=b+n;
       	else if(z==1)
            f[a+n][e[a+n]++]=b+n,f[b][e[b]++]=a,g[b+n][h[b+n]++]=a+n,g[a][h[a]++]=b;
        else if(z==2)
            f[a][e[a]++]=b,f[b+n][e[b+n]++]=a+n,g[b][h[b]++]=a,g[a+n][h[a+n]++]=b+n;
        else
            f[a][e[a]++]=b+n,f[b][e[b]++]=a+n,g[b+n][h[b+n]++]=a,g[a+n][h[a+n]++]=b;
	}
	for(j=1;j<=2*n;++j) {
		p[j]=2;
       	if(!c[j])
            D(j);
	}
	for(i=r;i;--i)
        if(c[i])
            T(w[i]);
	for(j=1,k=0;j<=n;++j)
        if(p[j]==1)
            d[++k]=j;
	printf("%d\n",k);
	for(i=1;i<=k;++i)
       	printf("%d\n",d[i]);
    return 0;
}