#include 
#include 
using namespace std;

const int maxn = 100000;
vector graph[maxn];
int main()
{
    int n, m;
    cin >> n >> m;
    
    for(int i = 0; i < m; i++) {
        int a, b;
        cin >> a >> b;
        graph[a].push_back(b);
        graph[b].push_back(a);
    }
    
    
    int S, E;
    cin >> S >> E;
    
    queue q;
    q.push(S);
    q.push(0);
    vector visited(n, false);
    while(!q.empty()) {
        int node = q.front();
        q.pop();
        int dist = q.front();
        q.pop();
        
        if(node == E) {
            cout << dist << endl;
            break;
        }
        for(int i = 0; i < graph[node].size(); i++) {
            int neighbour = graph[node][i];
            if(!visited[neighbour]) {
                visited[neighbour] = true;
                q.push(neighbour);
                q.push(dist + 1);
            }
            
        }
        
    }
    

    return 0;

}