import numpy as np
import math

sound = {261.6: "C4", 294.3: "D4", 327.0: "E4", 348.8: "F4", 392.4: "G4", 436.0: "A4", 490.5: "B4"}

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

ans = ""
min_norm = math.inf

for freq, kind in sound.items():
    cycle = int(n/freq)
    b = a[:-cycle]-a[cycle:]
    norm = np.linalg.norm(b)
    if norm < min_norm:
        min_norm = norm
        ans = kind

print(ans)