#include "bits/stdc++.h"
using namespace std;
#define all(x) begin(x),end(x)
template<typename A, typename B> ostream& operator<<(ostream &os, const pair<A, B> &p) { return os << '(' << p.first << ", " << p.second << ')'; }
template<typename T_container, typename T = typename enable_if<!is_same<T_container, string>::value, typename T_container::value_type>::type> ostream& operator<<(ostream &os, const T_container &v) { string sep; for (const T &x : v) os << sep << x, sep = " "; return os; }
#define debug(a) cerr << "(" << #a << ": " << a << ")\n";
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int,int> pi;
const int mxN = 1e5+1, oo = 1e9;
string name[] = {"C4", "D4","E4","F4","G4","A4","B4"};
double freq[] = {261.6, 294.3, 327.0, 348.8,392.4,436.0,490.5};
const int K = 7;
int main() {
    #ifdef LOCAL
    freopen("c.in","r",stdin);
    #endif
    int n; cin >> n;
    vi a(n);
    
    for(auto& i : a) cin >> i;
    pair<double,string> best = {};
    for(int i=0;i<K;++i) {
        // convolution with itself
        int OFF = llround(n/freq[i]);
        double ans=0;
        for(int j=0;j+OFF<n;++j) {
            ans+=a[j]*a[j+OFF];
        }
        ans/=(n-OFF);
        // debug(ans);
        // debug(name[i]);
        best  = max(best,{ans,name[i]});
    }
    cout << best.second << '\n';
}