#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define endl "\n"
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
const vector<double> freqs{ 261.6, 294.3, 327.0, 348.8, 392.4, 436.0, 490.5 };
const vector<string> str{ "C4","D4","E4","F4","G4","A4","B4" };
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n; cin >> n;
	vector<long long>a(n);
	rep(i, n)cin >> a[i];
	int idx = -1;
	long long val = -1;
	rep(i, freqs.size()) {
		long long subval = 0;
		int diff = n / freqs[i];
		rep(j, n) {
			int nj = (j + diff) % n;
			subval += a[j] * a[nj];
		}
		if (chmax(val, subval)) idx = i;
	}
	cout << str[idx] << endl;
	return 0;
}