#include <cstdio>
#include <cstring>
#include <vector>
#include <algorithm>
using namespace std;
const int N = 2000 + 10;
int n, e, p, q, s, a[N];
vector<int> G[N];
bool l[N];
void DFS(int u) {
    l[u] = 1;
    for(int i=0; i<G[u].size(); i++)
        if(!l[G[u][i]])
            DFS(G[u][i]);
}
int main() {
    freopen("running.in", "r", stdin);
    freopen("running.out", "w", stdout);
    scanf("%d %d", &n, &e);
    for(int i=0; i<e; i++) {
        scanf("%d %d", &p, &q);
        G[p].push_back(q);
        G[q].push_back(p);
    }
    for(int i=2; i<n; i++) {
        memset(l, 0, sizeof(l));
        l[i] = 1;
        DFS(1);
        if(!l[n]) a[s++] = i;
    }
    printf("%d\n", s);
    for(int i=0; i<s; i++)
        printf("%d ", a[i]);
    printf("\n");
    return 0;
}