#include <fstream>
#include <vector>
#include <cstring>
#include <bitset>
#define nmax 1005
using namespace std;
ifstream in("critice.in");
ofstream out("critice.out");
vector <int> v[nmax];
bitset <nmax> uz,fi,en;
int x[nmax*10],y[nmax*10],z[nmax*10],niv[nmax];
int n,m,o,sol[nmax*10],nrsol;
int p,u,q[nmax],t[nmax];
int f[nmax][nmax],c[nmax][nmax];


int bfs() {

    int i,x,y;
    uz.reset();
    memset(q,0,sizeof(q));
    memset(t,0,sizeof(t));
    p=1;u=1;
    q[1]=1;
    while (p<=u) {
        x=q[p];
        for (i=0;i<v[x].size();i++) {
            y=v[x][i];
            if (uz[y]==0&&c[x][y]>f[x][y]) {
                t[y]=x;
                uz[y]=1;
                q[++u]=y;
            }
        }
        p++;
    }
    return uz[n];
}
void dfs(int x)
{
    int i;
    for (i=0;i<v[x].size();i++)
        if (niv[v[x][i]]>niv[x]+1) {
            niv[v[x][i]]=niv[x]+1;
            dfs(v[x][i]);
        }
}

bool compare(int a,int b)
{
    if (niv[a]!=niv[b])
        return niv[a]>niv[b];
    return a<b;

}
void create_solutions()
{
    int i;
    for (i=1;i<=n;i++) {
        if (fi[i]==1&&en[i]==1)
            sol[++nrsol]=i;
        else
            if (fi[i]==1&&en[i]==1)
                sol[++nrsol]=i;
    }
    out<<nrsol<<'\n';
    for (i=1;i<=nrsol;i++)
        out<<sol[i]<<'\n';


}
int main()
{
    int i,j;
    in>>n>>m;
    for (i=1;i<=m;i++) {
        in>>x[i]>>y[i]>>z[i];
        v[x[i]].push_back(y[i]);
        v[y[i]].push_back(x[i]);
    }
    for (i=1;i<n;i++)
        niv[i]=1<<20;
    dfs(n);
    for (i=1;i<=m;i++) {
        if (compare(x[i],y[i]))
            c[x[i]][y[i]]=z[i];
        else
            c[y[i]][x[i]]=z[i];
    }
    int x,y;
    while (bfs()) {
        for (i=0;i<v[n].size();i++) {
            x=v[n][i];
            if (uz[x]==0||c[x][n]<=f[x][n])
                continue;
            o=c[x][n]-f[x][n];
            while (t[x]) {
                o=min(o,c[t[x]][x]-f[t[x]][x]);
                x=t[x];
            }
            x=v[n][i];
            f[x][n]+=o;
            f[n][x]-=o;
            while (t[x]) {
                f[t[x]][x]+=o;
                f[x][t[x]]-=o;
                x=t[x];
            }
        }
    }
    //out<<sol<<'\n';
    int p,u;
    p=1;u=1;
    fi[1]=1;
    q[1]=1;
    while (p<=u) {
        x=q[p];
        for (i=0;i<v[x].size();i++) {
            y=v[x][i];
            if (fi[y]==0&&c[x][y]>f[x][y]) {
                fi[y]=1;
                q[++u]=y;
            }
        }
        p++;
    }
    p=1;u=1;
    en[n]=1;
    q[1]=1;
    while (p<=u) {
        x=q[p];
        for (i=0;i<v[x].size();i++) {
            y=v[x][i];
            if (en[y]==0&&c[x][y]>f[x][y]) {
                en[y]=1;
                q[++u]=y;
            }
        }
        p++;
    }
    create_solutions();

    return 0;
}