#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (int)(n); i++)

using namespace std;

int main(){
    int N;
    cin >> N;
    vector<int> A(N);
    rep(i,N) cin >> A[i];
    
    string code[7] = {"C4", "D4", "E4", "F4", "G4", "A4", "B4"};
    int f[7] = {2616, 2943, 3270, 3488, 3924, 4360, 4905};
    int max_dif[7] = {0};
    vector<vector<int>> val(7);
    
    rep(i,7){
        rep(j,8){
            val[i].emplace_back(A[j*f[i]]);
        }
    }
    rep(i,7) sort(val[i].begin(), val[i].end());
    rep(i,7) max_dif[i] = val[i][7] - val[i][0];
    int ans = -1, res = 1e9;
    rep(i,7){
        if(max_dif[i] < res){
            res = max_dif[i];
            ans = i;
        }
    }
    cout << code[ans] << endl;
    
    return 0;
}