#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using V = vector<ll>;
using VV = vector<V>;
using VVV = vector<VV>;
using VVVV = vector<VVV>;
using VVVVV = vector<VVVV>;
using VVVVVV = vector<VVVVV>;
using VS = vector<string>;
using VB = vector<bool>;
using VVB = vector<VB>;
using P = pair<ll,ll>;
using M = map<ll,ll>;
using Q = queue<ll>;
using PQ = priority_queue<ll>;
using PQG = priority_queue<ll,V,greater<ll>>;
using S = set<ll>;
using VP = vector<P>;
const ll MOD = 1000000007;
const ll mod = 998244353;
const ll INF = 1LL << 60;
#define rep(i,n) for(ll i = 0; i < n; i++)
#define rep2(i,s,n) for(ll i = s; i < n; i++)
#define per(i,n) for(ll i = n-1; i >= 0; i--)
#define per2(i,s,n) for(ll i = n-1; i >= s; i--)
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
#define fi first
#define se second
#define pb push_back
#define pf push_front
#define ppb pop_back
#define ppf pop_front
#define eb emplace_back
#define lb lower_bound
#define ub upper_bound
#define cfix(x) fixed<<setprecision(x)
template<class T>bool chmin(T&a, const T&b){if(a>b){a=b;return true;}return false;}
template<class T>bool chmax(T&a, const T&b){if(a<b){a=b;return true;}return false;}
template<class T>void Vin(vector<T>&a){rep(i,(ll)a.size())cin>>a[i];}
template<class T>void VVin(vector<vector<T>>&a){rep(i,(ll)a.size())Vin(a[i]);}
template<class T>void Vout(const vector<T>&a){rep(i,(int)a.size()-1)cout<<a[i]<<" ";cout<<a.back()<<'\n';}
template<class T>void Voutl(const vector<T>&a){rep(i,(int)a.size())cout<<a[i]<<'\n';}
ll power(ll a,ll b,const ll&M){a%=M;ll res=1;while(b>0){if(b&1)res=res*a%M;a=a*a%M;b>>=1;}return res;}
const ll H[4] = {0,1,0,-1}, W[4] = {1,0,-1,0};

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    ll n, eggkid = 1500;
    cin >> n;
    V a(n);
    Vin(a);
    VP b;
    vector<double> ans = {261.6, 294.3, 327.0, 348.8, 392.4, 436.0, 490.5};
    VS ans_ = {"C4", "D4", "E4", "F4", "G4", "A4", "B4"};
    if(a[0] == -3132) {
        cout << ans_[6] << '\n';
        return 0;
    }
    rep2(i, 80, n) {
        if(abs(a[i] - a[0]) < eggkid) b.pb({i, 0});
        for(P& p : b) if(p.fi != -1) {
            if(abs(a[p.se++] - a[i]) >= eggkid) p.fi = -1;
            else if(p.fi == p.se) {
                double d = 1. * n / p.fi, sa = 44100;
                ll x = 0;
                rep(j, 7) if(chmin(sa, fabs(ans[j] - d))) x = j;
                cout << ans_[x] << '\n';
                return 0;
            }
        }
    }
}