from cmath import exp
from math import tau
n = int(input())
a = list(map(int, input().split()))

mx = 0.0
ans = -1

for i, freq in enumerate([261.6, 294.3, 327.0, 348.8, 392.4, 436.0, 490.5]):
    s = 0
    s += abs(sum(a[t] * exp(- t / n * freq * tau * 1j) for t in range(n)).real)
    r = int(n / freq / 4)
    s += abs(sum(a[(t + r) % n] * exp(- t / n * freq * tau * 1j) for t in range(n)).real)
    if s > mx:
        mx = s
        ans = i

print(['C4', 'D4', 'E4', 'F4', 'G4', 'A4', 'B4'][ans])