#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <map>
#include <set>
#include <fstream>
#include <cmath>
#include <stack>
#include <queue>
#include <iomanip>
#include <bitset>
using namespace std;

int main(){
    int n;cin>>n;
    vector<long long> a(n);
    int c = 0;
    int left = 0;
    int right = 0;
    for(int i=0;i<n;i++) {
        cin >> a[i];
        if(c==0 && a[i-1]<0 && 0<a[i]) {
            left = i;
            c++;
        }
        if(c==1 && a[i-1]<0 && 0<a[i]){
            right = i;
            c++;
        }
    }
    double diff = right - left;
    double f = 44100 / diff;

    vector<double> flist{261.6,294.3,327.0,348.8};
    vector<string> list{"C4","D4","E4","F4","G4","A4","B4"};
    double minv = 10000000000000;
    int ans = 0;
    for(int i = 0;i<flist.size();i++){
        if(abs(flist[i]-f) < minv){
            minv = abs(flist[i]-f);
            ans = i;
        }
    }
    cout << list[ans] << endl;

}