import sys

# sys.setrecursionlimit(10 ** 9)  # Codeforcesでは350000程度に


def input():
    return sys.stdin.readline().strip()


n = int(input())
A = list(map(int, input().split()))

# f0 = open("1905_sample/01_sample_03.in", "r")
# n = int(f0.readline())
# A = list(map(int, f0.readline().split()))

B = [261.6, 294.3, 327.0, 348.8, 392.4, 436.0, 490.5]
ANS = ["C4", "D4", "E4", "F4", "G4", "A4", "B4"]
C = [0] * len(B)

for i in range(len(B)):
    rb = n // round(B[i])
    for k in range(200):
        A0 = A[k : rb + k]
        A1 = A[rb + k : rb * 2 + k]
        r = 0
        for j in range(rb):
            r += abs(A0[j] - A1[j])
        r //= rb
        C[i] += r

# print(C)
ind = C.index(min(C))
print(ANS[ind])