import sys
from sys import stdin
import math
import random

def get(idx):

    i = int(idx)
    rem = idx - i
    if i + 1 >= len(A) or i < 0:
        return None

    ret = A[i] * (1-rem) + A[i+1] * rem
    return ret

N = int(stdin.readline())

A = list(map(int,stdin.readline().split()))

DF = [261.6,294.3, 327.0, 348.8, 392.4, 436.0, 490.5]
DN = ["C4", "D4", "E4", "F4", "G4", "A4", "B4"]

S = []

for freq in DF:

    ONE = N / freq
    nsum = 0
    nnum = 0
    diffmax = 0

    for i in range(10**5):

        L = random.uniform(0,N-1-ONE)

        catL = get(L)
        catR = get(L+ONE)

        
        if catL != None and catR != None:
            diffmax = max( diffmax , abs(catL - catR) )

    S.append( diffmax )

MI = min(S)

print (S,file=sys.stderr)

for i in range(6):
    if S[i] == MI:
        print (DN[i])
        break