#include <fstream>
#include <vector>

using namespace std;

const char InFile[]="party.in";
const char OutFile[]="party.out";
const int MaxN=205;

ifstream fin(InFile);
ofstream fout(OutFile);

int N,M,x,y,op,ind,comp,C[MaxN],low[MaxN],niv[MaxN],S[MaxN],SOL[MaxN];
vector<int> G[MaxN],GC[MaxN],El[MaxN];

void Tarjan(int nod)
{
	low[nod]=niv[nod]=++ind;
	S[++S[0]]=nod;
	for(vector<int>::iterator it=G[nod].begin();it!=G[nod].end();++it)
	{
		int &vcn=*it;
		if(!low[vcn])
		{
			Tarjan(vcn);
		}
		else if(low[vcn]>0)
		{
			if(low[vcn]<low[nod])
			{
				low[nod]=low[vcn];
			}
		}
	}
	
	if(low[nod]==niv[nod])
	{
		++comp;
		int tnod;
		do
		{
			tnod=S[S[0]];
			--S[0];
			C[tnod]=comp;
			low[tnod]=-low[tnod];
			El[comp].push_back(tnod);
		}while(tnod!=nod);
	}
}

void DFS(int nod)
{
	low[nod]=0;
	for(vector<int>::iterator it=GC[nod].begin();it!=GC[nod].end();++it)
	{
		int &vcn=*it;
		if(low[vcn])
		{
			DFS(vcn);
		}
	}
	S[++S[0]]=nod;
}

inline int NON(int x)
{
	if(x>=N)
	{
		return x-N;
	}
	return x+N;
}

int main()
{
	fin>>N>>M;
	for(register int i=1;i<=M;++i)
	{
		fin>>x>>y>>op;
		if(op==1)
		{
			y+=N;
		}
		else if(op==2)
		{
			x+=N;
		}
		else if(op==3)
		{
			y+=N;
			x+=N;
		}
		G[NON(x)].push_back(y);
		G[NON(y)].push_back(x);
	}
	fin.close();
	
	for(register int i=1;i<=(N<<1);++i)
	{
		if(!low[i])
		{
			Tarjan(i);
		}
	}
	
	for(register int i=1;i<=(N<<1);++i)
	{
		for(vector<int>::iterator it=G[i].begin();it!=G[i].end();++it)
		{
			GC[C[i]].push_back(C[*it]);
		}
	}
	
	for(register int i=1;i<=(N<<1);++i)
	{
		if(low[i])
		{
			DFS(i);
		}
	}
	
	while(S[0])
	{
		int c=S[S[0]];
		for(vector<int>::iterator it=El[c].begin();it!=El[c].end();++it)
		{
			int &nod=*it;
			if(SOL[nod]==0)
			{
				SOL[nod]=-1;
				SOL[NON(nod)]=1;
			}
		}
		--S[0];
	}
	
	int nrsol=0;
	for(register int i=1;i<=N;++i)
	{
		if(SOL[i]==1)
		{
			++nrsol;
		}
	}
	
	fout<<nrsol<<"\n";
	for(register int i=1;i<=N;++i)
	{
		if(SOL[i]==1)
		{
			fout<<i<<"\n";
		}
	}
	fout.close();
	return 0;
}