#include <bits/stdc++.h>

using namespace std;

vector<pair<int, int>> graf[512];

priority_queue<pair<int, pair<int, int>>, vector<pair<int, pair<int, int>>>, std::greater<pair<int, pair<int, int>>>> q;

int cost[512];

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    memset(cost, 0x3f3f3f3f, sizeof(cost));
    int t, l, o, d, temp;
    cin >> t >> l >> o >> d;
    vector<bool> marca(t, false);
    for(int i = 0; i < l; i++) {
        int k, uk;
        cin >> k >> uk;
        if(uk == o) {
            temp = i;
        }
        for(int j = 1; j < k; j++) {
            int v;
            cin >> v;
            if(v == o) {
                temp = i;
            }
            graf[uk].push_back(make_pair(v, i));
            graf[v].push_back(make_pair(uk, i));
        }
    }
    cost[o] = 1;
    q.push(make_pair(1, make_pair(o, temp)));
    while(!q.empty()) {
        pair<int, pair<int, int>> p = q.top();
        q.pop();
        int c = p.first, a = p.second.first;
        if(!marca[a]) {
            cost[a] = c;
            marca[a] = true;
            for(auto e : graf[a]) {
                int b = e.first, dd = e.second;
                if(!marca[b]) {
                    if(dd == p.second.second) {
                        q.push(make_pair(c, make_pair(b, dd)));
                    } else {
                        q.push(make_pair(c + 1, make_pair(b, dd)));
                    }
                }
            }
        }
    }
    cout << cost[d] << "\n";
    return 0;
}