#include <bits/stdc++.h>
#include <atcoder/modint>
using namespace std;
using namespace atcoder;
using ll = long long;
using mint =  modint1000000007;
#define rep(i,n) for (int i = 0; i < n; i++)
#define rrep(i,n) for (int i = n-1; i >= 0; i--)
#define rep2(i,a,b) for (int i = a; i < b; i++)
#define rrep2(i,a,b) for (int i = a-1; i >= b; i--)
#define rep3(i,a,b,c) for (int i = a; i < b; i+=c)
#define rrep3(i,a,b,c) for (int i = a-1; i >= b; i-=c)
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
template<class T> bool chmax(T &a, T b){if (a < b){a = b;return true;} else return false;}
template<class T> bool chmin(T &a, T b){if (a > b){a = b;return true;} else return false;}
template<class T> T power(T x, ll y){if (y == 0) return 1;T p = pow(x,y/2);if (y%2 == 0) return p*p;else return p*p*x;}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int n; cin >> n;
    vector<int> A(n);
    rep(i,n) cin >> A[i];
    vector<string> vs = {"C4", "D4", "E4", "F4", "G4", "A4", "B4"};
    vector<double> vd = {261.6, 294.3, 327.0, 348.8, 392.4, 436.0, 490.5};
    vector<int> cnt(7);
    rrep(i,1000){
        bool f = true;
        rep(j,i){
            bool g = false;
            rep2(k,-10,11){
                if (i+j+k >= 0 && i+j+k < n && abs(A[i+j+k]-A[j]) <= 500) g = true;
            }
            f = f && g;
        }
        if (f && i >= 88 && i <= 169){
            rep(j,7){
                if (abs(vd[j]-n/(double)i) <= 1){
                    cnt[j]++;
                }
            }
        }
    }
    int id = 0, ma = 0;
    rep(i,7) if (chmax(ma,cnt[i])) id = i;
    cout << vs[id] << endl;
}