#include <iostream>
#include <cstring>
#include <vector>
#include <cmath>
#include <queue>
using namespace std;
const int maxn = 1e5 + 10;
vector<int> graph[maxn];

int main() {
    ios_base::sync_with_stdio(false);
    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 + 1, false);

    visited[S] = true;

    int res = 0;
    while(!q.empty()) {
        int node = q.front();
        q.pop();
        int dist = q.front();
        q.pop();

        if(node == E) {
            res = dist;
            break;
        }

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

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

                visited[neighbour] = true;
            }


        }


    }

    cout << res << endl;
    return 0;
}