import sys

# sys.setrecursionlimit(200005)
int1 = lambda x: int(x)-1
pDB = lambda *x: print(*x, end="\n", file=sys.stderr)
p2D = lambda x: print(*x, sep="\n", end="\n\n", file=sys.stderr)
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def SI(): return sys.stdin.readline().rstrip()
dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
# dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
inf = (1 << 63)-1
# inf = (1 << 31)-1
# md = 10**9+7
md = 998244353

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

n = II()
aa = LI()
ans = ""
mn = inf
for h, s in zip(fr, ss):
    mx = 0
    for i in range(n):
        j = round(i+h)
        if j > n: break
        cur = abs(aa[i]-aa[j])
        if cur > mx: mx = cur
    if mx < mn: mn, ans = mx, s

print(ans)