use proconio::input;
fn main() {
    input! {
        n: usize,
        a: [usize; n],
    }
    if n == 1 {
        println!("No");
        return;
    }
    if n == 2 {
        if a[0] == a[1] {
            println!("Yes");
            return;
        } else {
            println!("No");
            return;
        }
    }
    for i in 0..n-2 {
        if a[i] == a[i+1] || a[i] == a[i+2] || a[i+1] == a[i+2] {
            println!("Yes");
            return;
        }
    }
    println!("No");
}