import sys
#input = sys.stdin.readline
#input = sys.stdin.buffer.readline #文字列はダメ
#sys.setrecursionlimit(1000000)
#import bisect
#import itertools
#import random
#from heapq import heapify, heappop, heappush
#from collections import defaultdict 
#from collections import deque
#import copy
import math
#from functools import lru_cache
#@lru_cache(maxsize=None)
#MOD = pow(10,9) + 7
#MOD = 998244353
#dx = [1,0,-1,0]
#dy = [0,1,0,-1]
#dx8 = [1,1,0,-1,-1,-1,0,1]
#dy8 = [0,1,1,1,0,-1,-1,-1]
#dx = [1,1,-1,-1]
#dy = [1,-1,1,-1]

def main():
    N = int(input())
    A = list(map(int,input().split()))
    ans = ["C4", "D4", "E4", "F4", "G4", "A4", "B4"]
    F = [261.6, 294.3, 327.0, 348.8, 392.4, 436.0, 490.5]

    idx = 0
    delta = pow(10,9)
    for i,f in enumerate(F):
        dif = int((1/f)/(1/N))
        #print(i,dif)
        #print(type(dif))
        temp = 0
        for j in range(N):
            nj = (j + dif)%N
            #print("i",i,"j",j,"dif",dif)
            #print(type(nj))
            #print(j,nj)
            temp += math.sqrt((A[j] - A[nj])**2)
        #print(temp,delta)
        if temp < delta:
            delta = temp
            idx = i
    print(ans[idx])



if __name__ == '__main__':
    main()