#include <cstdio>
#include <cstring>

#define file_in "party.in"
#define file_out "party.out"

#define Nmax 1010

int n,s[Nmax],m;
int x[Nmax],y[Nmax],z[Nmax];

int ok()
{
	int i;

	for (i=1;i<=m;++i)
	{
		if (z[i]==0)
		{
			if (s[x[i]]==0 && s[y[i]]==0) return 0;
		}
		if (z[i]==1)
		{
			if (s[x[i]]==0 && s[y[i]]==1) return 0;
		}
		if (z[i]==2)
		{
			if (s[x[i]]==1 && s[y[i]]==0) return 0;
		}
		if (z[i]==3)
		{
			if (s[x[i]]==1 && s[y[i]]==1) return 0;
		}
	}
	
	return 1;
}
	

void subm()   
{   
int q,x,i,nr,okk;   
s[n]=1;   
okk=1;
for (q=0;q<(1<<n)-1 && okk;++q)   
    {   
         
    x=n;   
    while (s[x])    
           {   
             s[x]=0;    
             x--;   
           }   
    s[x]=1;   
 	if (ok())
	{
		nr=0;
		for (i=1;i<=n;++i)
         if (s[i]) nr++;
        printf("%d\n", nr);
		for (i=1;i<=n;++i)
            if (s[i])
				printf("%d\n", i);
		okk=0;
    }   
}
}   


int main()
{
	int i;
	freopen(file_in,"r",stdin);
	freopen(file_out,"w",stdout);
	
	scanf("%d %d", &n,&m);
	for (i=1;i<=m;++i)
		 scanf("%d %d %d", &x[i],&y[i],&z[i]);
	
	subm();
	
	fclose(stdin);
	fclose(stdout);
	
	return 0;
}