use proconio::input;

fn main() {
    input! {
        n: usize,
        a: [i32; n],
    }

    if (0..n - 2).any(|i| a[i] == a[i + 1] || a[i] == a[i + 2] || a[i + 1] == a[i + 2]) {
        println!("Yes");
    } else {
        println!("No");
    }
}