use proconio::input;
fn main() {
    input! {
        n: usize,
        st: [(String, String); n],
    }
    for i in 0..n {
        let mut sflag = true;
        for j in 0..n {
            if i == j {
                continue;
            }
            if st[i].0 == st[j].0 || st[i].0 == st[j].1 {
                sflag = false;
                break;
            }
        }
        let mut tflag = true;
        for j in 0..n {
            if i == j {
                continue;
            }
            if st[i].1 == st[j].0 || st[i].1 == st[j].1 {
                tflag = false;
                break;
            }
        }
        if !sflag && !tflag {
            println!("No");
            return;
        }
    }
    println!("Yes");
}