BFS

/*    Never let anyone dull your sparkle...    */
#include <bits/stdc++.h>
using namespace std;

// type definition
#define int long long
using i64 = int64_t;
typedef pair<int, int> ii;
// constants
constexpr int N = 1e5 + 2;
constexpr int INF = 0x3f3f3f3f;
constexpr int MOD = 1e9 + 7;
constexpr float PI = 3.14;
// possible moves
constexpr int dx[8] = {1, 1, -1, -1, 0, 0, 1, -1};
constexpr int dy[8] = {1, 0, -1, 0, 1, -1, -1, 1};
// shortcuts
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define fi first
#define se second
#define endl '\n'
#define sz(x) i64(x.size())
#define all(x) begin(x), end(x)
#define rall(x) begin(x), end(x), greater<int>()
// loop definition
#define FOR(i, n, m) for (int i = n; i <= m; ++i)
#define FORD(i, n, m) for (int i = n; i >= m; --i)

vector<int> g[N];
queue<int> q;
bool used[N];
int d[N], parent[N];
int n, m;

void BFS(int s) {
    q.push(s);
    used[s] = true;
    parent[s] = -1;
    while (!q.empty()) {
        int u = q.front();
        q.pop();
        for (int v : g[u]) {
            if (!used[v]) {
                used[v] = true;
                q.push(v);
                d[v] = d[u] + 1;
                parent[v] = u;
            }
        }
    }
}

void PATH(int t) {
    if (!used[t])
        cout << "No path!" << endl;
    else {
        vector<int> path;
        for (int i = t; i != -1; i = parent[i]) path.pb(i);
        reverse(all(path));
        for (int i : path) cout << i << ' ';
    }
}
int32_t main(void) {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    //freopen("main.INP", "r", stdin);
    //freopen("main.OUT", "w", stdout);

    cin >> n >> m;
    int S, T; cin >> S >> T;
    while (m--) {
        int x, y; cin >> x >> y;
        g[x].pb(y);
        g[y].pb(x);
    }

    BFS(S);
    cout << d[T] << endl;
    PATH(T);
    return 0;
}