#include<cstdio>
#define N 1001
int p[N],n,m,i,a,b,j,w[N],c[N],nr,k,z,d[N],f[N][N],g[N][N],e[N],h[N];

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[++nr]=x;}

void T(int x)
{int i;
c[x]=0;
if(p[x]==2)
       {p[x]=0;
       if(x>n)
               p[x-n]=1;
       else
               p[x+n]=1;}
for(i=0;i<h[x];i++)
if(c[g[x][i]])
       T(g[x][i]);}

int main()
{FILE *f1=fopen("party.in","r"),*f2=fopen("party.out","w");
fscanf(f1,"%d%d",&n,&m);
while(m--)
       {fscanf(f1,"%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=nr;i;i--)
if(c[i])
       T(w[i]);
for(j=1,k=0;j<=n;j++)
if(p[j]==1)
       d[++k]=j;
fprintf(f2,"%d\n",k);
for(i=1;i<=k;i++)
       fprintf(f2,"%d\n",d[i]);
return 0;}