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

#define _P(...) (void)printf(__VA_ARGS__)
#define FOR(x,to) for(x=0;x<(to);x++)
#define FORR(x,arr) for(auto& x:arr)
#define FORR2(x,y,arr) for(auto& [x,y]:arr)
#define ALL(a) (a.begin()),(a.end())
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
template<class T> bool chmax(T &a, const T &b) { if(a<b){a=b;return 1;}return 0;}
template<class T> bool chmin(T &a, const T &b) { if(a>b){a=b;return 1;}return 0;}
//-------------------------------------------------------

int N;
double A[55555];
double S[]={261.6, 294.3, 327.0, 348.8, 392.4, 436.0, 490.5};
string pat[]={"C4", "D4", "E4", "F4", "G4", "A4", "B4"};

void solve() {
	int i,j,k,l,r,x,y; string s;
	
	cin>>N;
	FOR(i,N) {
		cin>>A[i];
		A[i]+=100000;
	}
	double dif[7]={};
	FOR(i,7) {
		double span=N/S[i];
		FOR(j,N-1000) {
			double a=A[j+(int)floor(span)];
			double b=A[j+(int)ceil(span)];
			double c;
			double p=a*(1-modf(span,&c))+b*modf(span,&c);
			dif[i]+=abs(p-A[j]);
		}
	}
	
	cout<<pat[min_element(dif,dif+7)-dif]<<endl;
	
}


int main(int argc,char** argv){
	string s;int i;
	if(argc==1) ios::sync_with_stdio(false), cin.tie(0);
	FOR(i,argc-1) s+=argv[i+1],s+='\n'; FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin);
	cout.tie(0); solve(); return 0;
}