fn main() {
    let n : usize = input();
    let a : Vec<i64> = input_vec();

    let mut diff = Vec::new();
    for f in vec![261, 294, 327, 349, 392, 436, 490] {
        let f = n / f;
        let mut d = 0;
        for i in 0..n-f {
            d += (a[i] - a[i + f]).abs();
        }
        diff.push(d);
    }

    let min = *diff.iter().min().unwrap();
    let ans = diff.iter().position(|&d| d == min).unwrap();

    let s = vec!["C4", "D4", "E4", "F4", "G4", "A4", "B4"];
    println!("{}", s[ans]);
}

#[allow(dead_code)] fn input<T: std::str::FromStr>() -> T { let mut s = String::new(); std::io::stdin().read_line(&mut s).ok(); s.trim().parse().ok().unwrap() } #[allow(dead_code)] fn input_t<T: std::str::FromStr, U: std::str::FromStr>() -> (T, U) { let mut s = String::new(); std::io::stdin().read_line(&mut s).ok(); let s = s.trim().split_whitespace().collect::<Vec<&str>>(); (s[0].parse().ok().unwrap(), s[1].parse().ok().unwrap()) } #[allow(dead_code)] fn input_t3<T1: std::str::FromStr, T2: std::str::FromStr, T3: std::str::FromStr>() -> (T1, T2, T3) { let mut s = String::new(); std::io::stdin().read_line(&mut s).ok(); let s = s.trim().split_whitespace().collect::<Vec<&str>>(); (s[0].parse().ok().unwrap(), s[1].parse().ok().unwrap(), s[2].parse().ok().unwrap()) } #[allow(dead_code)] fn input_t4<T1: std::str::FromStr, T2: std::str::FromStr, T3: std::str::FromStr, T4: std::str::FromStr>() -> (T1, T2, T3, T4) { let mut s = String::new(); std::io::stdin().read_line(&mut s).ok(); let s = s.trim().split_whitespace().collect::<Vec<&str>>(); (s[0].parse().ok().unwrap(), s[1].parse().ok().unwrap(), s[2].parse().ok().unwrap(), s[3].parse().ok().unwrap()) } #[allow(dead_code)] fn input_t5<T1: std::str::FromStr, T2: std::str::FromStr, T3: std::str::FromStr, T4: std::str::FromStr, T5: std::str::FromStr>() -> (T1, T2, T3, T4, T5) { let mut s = String::new(); std::io::stdin().read_line(&mut s).ok(); let s = s.trim().split_whitespace().collect::<Vec<&str>>(); (s[0].parse().ok().unwrap(), s[1].parse().ok().unwrap(), s[2].parse().ok().unwrap(), s[3].parse().ok().unwrap(), s[4].parse().ok().unwrap()) } #[allow(dead_code)] fn input_vec<T: std::str::FromStr>() -> Vec<T> { let mut s = String::new(); std::io::stdin().read_line(&mut s).ok(); s.trim().split_whitespace().map(|s| s.parse().ok().unwrap()).collect() }