#include <iostream>
#include <vector>
#include <queue>
using namespace std;
const int maxn = 1e5 + 5;
int n, m;
vector<int> graph[maxn];

void bfs(int S, int E) {
    queue<pair<int, int>> q;
    q.push({S, 0});

    vector<bool> visited(n + 1, false);
    visited[S] = true;

    while(!q.empty()) {
        int node = q.front().first;
        int dist = q.front().second;
        q.pop();

        if(node == E) {
            cout << dist << endl;
            break;
        }

        for(int neighbour : graph[node]) {
            if(!visited[neighbour]) {
                visited[neighbour] = true;
                q.push({neighbour, dist + 1});
            }
        }

    }
}
int main() {
    ios_base::sync_with_stdio(false);

    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;
    bfs(S, E);
    return 0;
}