#include<bits/stdc++.h>
using namespace std;

vector<int>node[10000];
int parent[10000];

int bfc(int source,int destination)
{
    queue<int>q;
    int arr[10000],dis;
    q.push(source);
    arr[source] = 1;
    parent[source] = -1;
    while(!q.empty()){
        int n;
        n = q.front();
        q.pop();
        for(int i = 0 ; i < node[n].size() ; i++ ){
            if(node[n][i] == destination){dis = arr[n];parent[destination] = n;return dis;}
            if(arr[node[n][i]] == NULL ){
                arr[node[n][i]] = arr[n] + 1;
                parent[node[n][i]] = n;
                q.push(node[n][i]);
            }
        }
    }
}

int main()
{
    int num_nodes,num_edges;

    cin >> num_nodes >> num_edges;

    for(int i = 0 ; i < num_edges ; i++){
        int x , y;
        cin >> x >> y;

        node[x].push_back(y);
        node[y].push_back(x);
    }
    int beg,last;
    cin >> beg >> last;
    cout << bfc(beg,last)<<endl;
    int n = last;
    while(parent[n] != -1 ){
        cout << n << " <- ";
        n = parent[n];
    }cout << beg << endl;

    return 0;

}