#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
using ll=long long;
using Graph=vector<vector<int>>;
#define INF 1000000000
#define MOD 998244353
#define MAX 1000

int main(){
  int N;
  cin>>N;
  vector<int> A(N);
  for(int i=0;i<N;i++){
    cin>>A[i];
  }
  vector<int> zero_point;
  for(int i=0;i<N;i++){
    if(A[i]==0){
      zero_point.push_back(2*i);
    }
  }
  for(int i=1;i<N;i++){
    if(A[i-1]*A[i]<0){
      zero_point.push_back(2*i-1);
    }
  }
  sort(zero_point.begin(),zero_point.end());

  int n=zero_point.size();
  double f=1.0/(((double)A[n-1]-(double)A[0])/((double)n-1.0));

  double epsilon=1.0e-2;
  vector<double> hel(7);
  hel[0]=261.6;
  hel[1]=294.3;
  hel[2]=327.0;
  hel[3]=348.0;
  hel[4]=392.4;
  hel[5]=436.0;
  hel[6]=490.5;
  vector<string> ans(7);
  ans[0]="C4";
  ans[1]="D4";
  ans[2]="E4";
  ans[3]="F4";
  ans[4]="G4";
  ans[5]="A4";
  ans[6]="B4";
  for(int i=0;i<7;i++){
    if(abs(f-hel[i])/hel[i]<=epsilon){
      cout<<ans[i]<<endl;
    }
  }
}