#include <bits/stdc++.h>

using i32 = std::int32_t;
using u32 = std::uint32_t;
using i64 = std::int64_t;
using u64 = std::uint64_t;
using i128 = __int128_t;
using u128 = __uint128_t;

class Range {
    struct Iter {
        int itr;
        constexpr Iter(const int pos) noexcept : itr(pos) {}
        constexpr void operator++() noexcept { ++itr; }
        constexpr bool operator!=(const Iter& other) const noexcept { return itr != other.itr; }
        constexpr int operator*() const noexcept { return itr; }
    };
    const Iter first, last;

  public:
    explicit constexpr Range(const int first, const int last) noexcept : first(first), last(std::max(first, last)) {}
    constexpr Iter begin() const noexcept { return first; }
    constexpr Iter end() const noexcept { return last; }
};

constexpr Range rep(const int l, const int r) noexcept { return Range(l, r); }
constexpr Range rep(const int n) noexcept { return Range(0, n); }

template <class T, T Div = 2> constexpr T INFTY = std::numeric_limits<T>::max() / Div;

template <class T> constexpr bool setmin(T& lhs, const T& rhs) {
    if (lhs > rhs) {
        lhs = rhs;
        return true;
    }
    return false;
}

using std::array;
using std::pair;
using std::tuple;
using std::vector;

const std::string X[] = {"C4", "D4", "E4", "F4", "G4", "A4", "B4"};
const double Y[] = {261.6, 294.3, 327.0, 348.8, 392.4, 436.0, 490.5};

void main_() {
    int N;
    std::cin >> N;
    vector<int> A(N);
    for (auto& x : A) {
        std::cin >> x;
    }
    array<i64, 7> score = {};
    for (const int k : rep(7)) {
        const int shift = N / Y[k] + 0.5;
        for (const int j : rep(10)) {
            for (const int i : rep(N)) {
                const i64 x = A[i];
                const i64 y = A[(i + shift * j) % N];
                score[k] += (x - y) * (x - y);
            }
        }
    }
    std::cout << X[std::min_element(score.begin(), score.end()) - score.begin()] << '\n';
}

int main() {
    std::ios_base::sync_with_stdio(false);
    std::cin.tie(nullptr);
    main_();
    return 0;
}