vector<int> g[n];
int depth[n];
void bfs(int from){
    fill(depth,depth+n, inf);
    depth[0] = 0;
    queue<pair<int,int> > q;
    q.push({from,0});
    while(q.size()){
        auto [nxtv, nxtw] = q.front();
        q.pop();
        if(depth[nxtv] < nxtw) continue;
        for(int v : g[nxtv]){
            if(depth[nxtv] + 1 < depth[v]){
                depth[v] = depth[nxtv] + 1;
                q.push({v,depth[v]});
            }
        }
    }
}