import sys
input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#######################################################################

ni()
n = 44100
m = 500000
a = na()
def f(x):
    r = floor(x)
    #print(x-r,1-x+r)
    return a[r]*(x-r)+a[r+1]*(1-x+r)

z = [261.6, 294.3, 327.0, 348.0, 392.4, 436.0, 495.0]
from math import floor
from random import random as rand, randint

eps = 100

ans = []
for i in range(7):
    x = n/z[i]
    
    # xの周期があるか調べる
    r = floor(z[i])-1
    # r個の区間[0, x),[x,2*x],,,,[(r-1)x, rx)
    d = 0
    for i in range(m):
        p,q = randint(0,r-1),randint(0,r-1)
        y = rand()*x
        if abs(f(y+p*x)-f(y+q*x))<=eps:
            d += 1
    ans.append(d)
#print(ans)
p = ans.index(max(ans))
print(chr(p+65+2)+"4")