import std.stdio, std.algorithm, std.conv, std.array, std.string, std.math, std.typecons, std.numeric;

struct UFTree(T)
{
    struct Node
    {
        T parent;
        T rank = 1;
    }

    ///
    this(T n)
    {
        nodes.length = n;
        sizes.length = n;
        foreach (i, ref node; nodes) {
            node = Node(i.to!T);
            sizes[i] = 1;
        }
    }

    ///
    bool unite(T a, T b)
    {
        a = root(a);
        b = root(b);

        if (a == b) return false;

        if (nodes[a].rank < nodes[b].rank) {
            sizes[nodes[a].parent] += sizes[nodes[b].parent];
            nodes[b].parent = nodes[a].parent;
        } else {
            sizes[nodes[b].parent] += sizes[nodes[a].parent];
            nodes[a].parent = nodes[b].parent;
            if (nodes[a].rank == nodes[b].rank) nodes[a].rank += 1;
        }

        return true;
    }

    ///
    bool is_same(T a, T b)
    {
        return root(a) == root(b);
    }

    ///
    T size(T i)
    {
        return sizes[root(i)];
    }

private:
    Node[] nodes;
    T[] sizes;

    T root(T i)
    {
        if (nodes[i].parent == i) return i;

        return nodes[i].parent = root(nodes[i].parent);
    }
}

///
UFTree!T uftree(T)(T n)
{
    return UFTree!T(n);
}

void main()
{
    auto nm = readln.split.to!(int[]);
    auto N = nm[0];
    auto M = nm[1];

    auto uft = uftree(N+M);

    foreach (int n; 0..N) {
        foreach (l; readln.split.to!(int[])[1..$]) {
            uft.unite(n, l-1);
        }
    }

    foreach (int i; 0..N-1) {
        if (!uft.is_same(i, i+1)) {
            writeln("NO");
            return;
        }
    }
    writeln("YES");
}