// Input macro
macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
    ($($r:tt)*) => {
        let s = {
            use std::io::Read;
            let mut s = String::new();
            std::io::stdin().read_to_string(&mut s).unwrap();
            s
        };
        let mut iter = s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
}
 
macro_rules! stdin {
    () => {{
        use std::io::Read;
        let mut s = String::new();
        std::io::stdin().read_to_string(&mut s).unwrap();
        s
    }};
}
 
macro_rules! input_inner {
    ($iter:expr) => {};
    ($iter:expr, ) => {};
 
    ($iter:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($iter, $t);
        input_inner!{$iter $($r)*}
    };
}
 
macro_rules! read_value {
    ($iter:expr, ( $($t:tt),* )) => {
        ( $(read_value!($iter, $t)),* )
    };
 
    ($iter:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()
    };
 
    ($iter:expr, chars) => {
        read_value!($iter, String).chars().collect::<Vec<char>>()
    };
 
    ($iter:expr, usize1) => {
        read_value!($iter, usize) - 1
    };
 
    ($iter:expr, $t:ty) => {
        $iter.next().unwrap().parse::<$t>().expect("Parse error")
    };
}
 
// Test Code
macro_rules! test {
    ($($input:expr => $output:expr),* $(,)*) => {
        #[test]
        fn solve_test() {
            $(
                assert_eq!(solve($input), $output);
            )*
        }
    };
}
 
test! {
    // テストコードをここにコピペする
r"3
7 9 6 8
2 8 5 8
3 9 4 8" => "YES",
 
}
 
fn main() {
    println!("{}", solve(&stdin!()));
}
 
fn solve(src: &str) -> String {
    input! {
        source = src,
        n: i32,    // 問題に合わせて記述
        procs: [[(i32,i32); 2]; n]
    }
    let mut a = (2,8);
    let mut b = (3,9);
    let mut c = (7,9);
    for proc in procs {
        match proc[0] {
            given if given == a => a = proc[1],
            given if given == b => b = proc[1],
            given if given == c => c = proc[1],
            _ => continue
        };
    }
    if a == (5,8) && b == (4,8) && c == (6,8) {
        return "YES".to_string();
    } else {
        return "NO".to_string();
    } 
}