#include <iostream>
#include <queue>
using namespace std;

const int maxn = 100000;
vector<int> 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<int> q;
    q.push(S);
    q.push(0);
    vector<bool> 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;

}