use proconio::input;

fn main() {
	input! {
		n: usize,
		a: [usize; n],
	}

    for i in 0..n-1 {
        if a[i] == a[i+1] {
            println!("Yes");
            return;
        }
    }


    for i in 0..n-2 {
        if a[i] == a[i+2] {
            println!("Yes");
            return;
        }
    }

    println!("No");	
}