Linhas de Ônibus

#include <bits/stdc++.h>
using namespace std;

int G[580][580];

int32_t main() {
    int t, l, o, d;

    cin >> t >> l >> o >> d; o--; d--;

    while(l--) {
        int c;
        cin >> c;
        vector<int> L(c);
        for(int j = 0; j < c; j++)
            cin >> L[j], L[j]--;
        for(int j = 0; j < c; j++)
            for(int k = j + 1; k < c; k++)
                G[L[j]][L[k]] = G[L[k]][L[j]] = 1;
    }

    queue<int> q;
    vector<int> dist(t + 1, -1);

    dist[o] = 0;
    q.push(o);

    while(!q.empty()) {
        int u = q.front();
        q.pop();
        for(int w = 0; w < t; w++)
            if(G[u][w] and dist[w] == -1) {
                dist[w] = dist[u] + 1;
                q.push(w);
            }
    }
    cout << dist[d] << '\n';

    return 0;
}