#include <bits/stdc++.h>

using namespace std;


int main()
{
    int n, m;
    cin >> n >> m;
    vector<vector<int> > elek(m, vector<int>());
    for (int i=0; i<n; i++) {
        int x, y;
        cin >> x >> y;
        x--;
        y--;
        elek[x].push_back(y);
        elek[y].push_back(x);
    }

    queue<pair<int, int> > sor;
    sor.push({0, m-1});
    vector<int> ertekek(m, -1);

    while (sor.size()>0) {

        int tav=sor.front().first;
        int elso=sor.front().second;
        sor.pop();
        if (ertekek[elso]!=-1) {
            continue;
        }
        //cout << elso << " " << tav << "\n";
        ertekek[elso]=tav;
        for (int sz : elek[elso]) {
            sor.push({tav+1, sz});
        }
    }
    if (ertekek[0]==-1) {
        cout << "-1";
    }
    else {
        cout << ertekek[0]-1 << "\n";
        int szam=ertekek[0];
        for (int i=1; i<m; i++) {
                if (szam==0) {
                    break;
                }
            if (ertekek[i]<=ertekek[0] && ertekek[i]!=-1) {
                cout << i+1 << " ";
                szam--;
            }
        }
    }


    return 0;
}