#include <iostream>
#include <vector>
#include <queue>
using namespace std;
const int maxn = 1e5 + 10;

vector<int> graph[maxn];
int main() {
    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); // one directioanl
        graph[b].push_back(a); // two directioanal
    }
    int S, E;
    cin >> S >> E;
    queue<int> q;

    q.push(S);
    q.push(0);

    vector<bool> visited(num_of_vertices + 1, 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 < (int) graph[node].size(); i++) {
            int neighbour = graph[node][i];
            if(!visited[neighbour]) {
                visited[neighbour] = true;
                q.push(neighbour);
                q.push(dist + 1);
            }
        }

    }

    return 0;
}