#include <iostream>
#include <vector>
#include <queue>
using namespace std;
const int maxn = 100005;
vector<int> graph[maxn];
int main() {
    ios_base::sync_with_stdio(false);
    int num_of_vertices;
    cin >> num_of_vertices;

    int num_of_edges;
    cin >> num_of_edges;

    for(int i = 0; i < num_of_edges; i++) {
        int a, b;
        cin >> a >> b;
        graph[a].push_back(b);
        graph[b].push_back(a);
    }
    int S, E;
    cin >> S >> E;

    queue<int> q;
    q.push(S);
    q.push(0);

    vector<bool> visited(num_of_vertices, false);

    while(!q.empty()) {
        int c_node = q.front();
        q.pop();
        int dist = q.front();
        q.pop();

        if(c_node == E) {
            cout << dist << endl;
            return 0;
        }

        for(int i = 0; i < graph[c_node].size(); i++) {
            int neighbour = graph[c_node][i];

            if(!visited[neighbour]) {
                q.push(neighbour);
                q.push(dist + 1);
                visited[neighbour] = true;
            }
        }
    }

    cout << 0 << endl;



    return 0;
}