#include<cstdio>
#include<vector>
#include<bitset>
#include<cstring>

using namespace std;
const int nmax = 105;
int n,m,i,x,y,z,tsort[2*nmax],cnt,comp[2*nmax],sol;
vector<int> v[2*nmax];
vector<int> vt[2*nmax];
bool viz[2*nmax];

#define v (v+nmax)
#define vt (vt+nmax)
#define comp (comp+nmax)
#define viz (viz+nmax)

void dfs(int x)
{
    viz[x]=1;
    for(vector<int>::iterator it=v[x].begin();it!=v[x].end();it++)
        if(!viz[*it]) dfs(*it);
    tsort[++cnt]=x;
}

void dfst(int x)
{
    viz[x]=1; comp[x]=cnt;
    for(vector<int>::iterator it=vt[x].begin();it!=vt[x].end();it++)
        if(!viz[*it]) dfst(*it);
}

int main()
{
	freopen("party.in","r",stdin);
	freopen("party.out","w",stdout);
	scanf("%d%d",&n,&m);
	for(;m;m--)
	{
	    scanf("%d%d%d",&x,&y,&z);
	    if(z==1) y=-y;
	    else if(z==2) x=-x;
	    else if(z==3) x=-x,y=-y;
	    v[-x].push_back(y);
        v[-y].push_back(x);
        vt[y].push_back(-x);
        vt[x].push_back(-y);
	}

	for(i=-n;i<=n;i++) if(!viz[i] && i) dfs(i);
    for(i=-n;i<=n;i++) viz[i]=0; cnt=0;
    for(i=2*n;i;i--) if(!viz[tsort[i]]) {cnt++; dfst(tsort[i]);}

    for(i=1;i<=n;i++) if(comp[i]>comp[-i]) sol++; printf("%d\n",sol);
    for(i=1;i<=n;i++) if(comp[i]>comp[-i]) printf("%d\n",i);

	return 0;
}