// -*- coding:utf-8-unix -*-

#![allow(dead_code)]
#![allow(unused_imports)]

use std::cmp::*;
use std::collections::*;
use std::fs::File;
use std::io::prelude::*;
use std::io::*;
use std::mem;
use std::str;
use std::vec;

const INF: i64 = 1223372036854775807;
const MEM_SIZE: usize = 202020;
const MOD: i64 = 1000000007;
// const MOD: i64 = 998244353;

use std::cmp::*;
use std::collections::*;
use std::io::stdin;
use std::io::stdout;
use std::io::Write;
#[allow(dead_code)]
fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}

#[allow(dead_code)]
fn readi() -> (i64) {
    let mut str = String::new();
    let _ = stdin().read_line(&mut str).unwrap();
    let mut iter = str.split_whitespace();
    iter.next().unwrap().parse::<i64>().unwrap()
}

#[allow(dead_code)]
fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>()
        .split_whitespace()
        .map(|e| e.parse().ok().unwrap())
        .collect()
}
#[allow(dead_code)]
fn read_vec2<T: std::str::FromStr>(n: u32) -> Vec<Vec<T>> {
    (0..n).map(|_| read_vec()).collect()
}

#[allow(dead_code)]
fn readii() -> (i64, i64) {
    let mut str = String::new();
    let _ = stdin().read_line(&mut str).unwrap();
    let mut iter = str.split_whitespace();
    (
        iter.next().unwrap().parse::<i64>().unwrap(),
        iter.next().unwrap().parse::<i64>().unwrap(),
    )
}

#[allow(dead_code)]
fn readiii() -> (i64, i64, i64) {
    let mut str = String::new();
    let _ = stdin().read_line(&mut str).unwrap();
    let mut iter = str.split_whitespace();
    (
        iter.next().unwrap().parse::<i64>().unwrap(),
        iter.next().unwrap().parse::<i64>().unwrap(),
        iter.next().unwrap().parse::<i64>().unwrap(),
    )
}
#[allow(dead_code)]
fn readuu() -> (usize, usize) {
    let mut str = String::new();
    let _ = stdin().read_line(&mut str).unwrap();
    let mut iter = str.split_whitespace();
    (
        iter.next().unwrap().parse::<usize>().unwrap(),
        iter.next().unwrap().parse::<usize>().unwrap(),
    )
}

#[allow(dead_code)]
fn readuuu() -> (usize, usize, usize) {
    let mut str = String::new();
    let _ = stdin().read_line(&mut str).unwrap();
    let mut iter = str.split_whitespace();
    (
        iter.next().unwrap().parse::<usize>().unwrap(),
        iter.next().unwrap().parse::<usize>().unwrap(),
        iter.next().unwrap().parse::<usize>().unwrap(),
    )
}

#[allow(dead_code)]
fn readuuuu() -> (usize, usize, usize, usize) {
    let mut str = String::new();
    let _ = stdin().read_line(&mut str).unwrap();
    let mut iter = str.split_whitespace();
    (
        iter.next().unwrap().parse::<usize>().unwrap(),
        iter.next().unwrap().parse::<usize>().unwrap(),
        iter.next().unwrap().parse::<usize>().unwrap(),
        iter.next().unwrap().parse::<usize>().unwrap(),
    )
}

pub struct Dsu {
    n: usize,
    // root node: -1 * component size
    // otherwise: parent
    parent_or_size: Vec<i32>,
}

impl Dsu {
    // 0 <= size <= 10^8 is constrained.
    pub fn new(size: usize) -> Self {
        Self {
            n: size,
            parent_or_size: vec![-1; size],
        }
    }
    pub fn merge(&mut self, a: usize, b: usize) -> usize {
        assert!(a < self.n);
        assert!(b < self.n);
        let (mut x, mut y) = (self.leader(a), self.leader(b));
        if x == y {
            return x;
        }
        if -self.parent_or_size[x] < -self.parent_or_size[y] {
            std::mem::swap(&mut x, &mut y);
        }
        self.parent_or_size[x] += self.parent_or_size[y];
        self.parent_or_size[y] = x as i32;
        x
    }

    pub fn same(&mut self, a: usize, b: usize) -> bool {
        assert!(a < self.n);
        assert!(b < self.n);
        self.leader(a) == self.leader(b)
    }
    pub fn leader(&mut self, a: usize) -> usize {
        assert!(a < self.n);
        if self.parent_or_size[a] < 0 {
            return a;
        }
        self.parent_or_size[a] = self.leader(self.parent_or_size[a] as usize) as i32;
        self.parent_or_size[a] as usize
    }
    pub fn size(&mut self, a: usize) -> usize {
        assert!(a < self.n);
        let x = self.leader(a);
        -self.parent_or_size[x] as usize
    }
    pub fn groups(&mut self) -> Vec<Vec<usize>> {
        let mut leader_buf = vec![0; self.n];
        let mut group_size = vec![0; self.n];
        for i in 0..self.n {
            leader_buf[i] = self.leader(i);
            group_size[leader_buf[i]] += 1;
        }
        let mut result = vec![Vec::new(); self.n];
        for i in 0..self.n {
            result[i].reserve(group_size[i]);
        }
        for i in 0..self.n {
            result[leader_buf[i]].push(i);
        }
        result
            .into_iter()
            .filter(|x| !x.is_empty())
            .collect::<Vec<Vec<usize>>>()
    }
}

fn solve() {
    let (n, m) = readuu();
    let mut data = vec![vec![0 as usize; (0) as usize]; (m) as usize];
    let mut dsu = Dsu::new(n);
    for i in 0..n {
        let vec: Vec<usize> = read_vec();
        for j in 1..vec.len() {
            data[vec[j] - 1].push(i);
        }
    }
    // println!("{:?}", data);
    for i in 0..m {
        if (data[i].is_empty()) {
            continue;
        }
        for j in 0..data[i].len() - 1 {
            dsu.merge(data[i][j], data[i][j + 1]);
        }
    }

    let mut flg = true;
    for i in 0..n - 1 {
        if dsu.same(i, i + 1) == false {
            flg = false;
        }
    }
    if flg {
        println!("YES");
    } else {
        println!("NO");
    }
}
fn main() {
    solve()
}


Measured memory_bytes: 6492