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

shikii = round(max(a) * 0.9)

peek = []
for i in range(100, n - 100):
    if a[i] >= shikii and a[i - 1] < a[i] and a[i] > a[i + 1]:
        peek.append(i)

l = len(peek)
f = 0
for i in range(l - 1):
    f += n / (peek[i + 1] - peek[i])
assert l >= 1
f = f / (l - 1)

sa = 10 ** 9
ans = None
li = [(261.6, 'C4'), (294.3, 'D4'), (327.0, 'E4'), (348.8, 'F4'), (392.4, 'G4'), (436.0, 'A4'), (490.5, 'B4')]

for v, c in li:
    if abs(f - v) < sa:
        sa = abs(f - v)
        ans = c
print(ans)