// \sum_i sgn(A_i)sgn(B_i) 最大化
#include <iostream>
#include <vector>
using namespace std;

const vector<double> freqs{261.6, 294.3, 327.0, 348.8, 392.4, 436.0, 490.5};

template <class T>
int sgn(T x) {
    if (x > 0) return 1;
    if (x < 0) return -1;
    return 0;
}

int main() {
    cin.tie(nullptr), ios::sync_with_stdio(false);

    int N;
    cin >> N;
    vector<short> A(N);
    for (auto &x : A) cin >> x;

    int bestscore = -100000000;
    int argbest = -1;
    for (int d = 0; d < freqs.size(); ++d) {
        int score = 0;

        // freq[d] Hz -> 長さ N で freq[d] 周期 -> 一周期 period は N / freq[d] 要素分
        int period = N / freqs[d];

        for (int i = 0; i < N / 2; ++i) {
            score += sgn(A[i]) * sgn(A[i + period]);
        }
        if (score > bestscore) {
            bestscore = score;
            argbest = d;
        }
    }
    cout << (char)('A' + (2 + argbest) % 7) << "4\n";
}