#include <cstdio>
#include <vector>

#define NMAX 100001
#define pb push_back

using namespace std;

vector <int> v[NMAX];

bool ap[NMAX];
int n,m,nrcomp;

inline void df(int nod){
    ap[nod]=1;
    for (auto it:v[nod])
        if (!ap[it])df(it);

    printf("%d ",nod);
}

int main()
{
    freopen("dfs.in","r",stdin);
    freopen("dfs.out","w",stdout);

    int x,y;

    scanf("%d %d\n",&n,&m);
    for (int i=1;i<=m;i++){
        scanf("%d %d",&x,&y);
        v[x].pb(y);
        v[y].pb(x);
    }
    for (int i=1;i<=n;i++)
        if (!ap[i])nrcomp++,df(i);

    printf("%d\n",nrcomp);

    fclose(stdin);
    fclose(stdout);
}