#include<bits/stdc++.h>
using namespace std;
using ll = long long;

int main(){
    int n;
    cin >> n;
    vector<int> hz={2616, 2943, 3270, 3488, 3924, 4360, 4905};
    vector<ll> a(n);
    vector<string> ans={"C4", "D4", "E4", "F4", "G4", "A4", "B4"};
    for(auto &&v:a)cin >> v;
    ll score = 0, pos = 0;
    for(int i = 0; i < hz.size(); i++){
        int priod = 10 * n / hz[i];
        ll sumv = 0;
        for(int j = 0; 2*j < n; j++){
            sumv += a[j] * a[j + priod];
        }
        if(sumv > score){
            score = sumv;
            pos = i;
        }
    }
    cout << ans[pos] << endl;
}