# coding: utf-8
# Your code here!
import sys
sys.setrecursionlimit(10**6)
readline = sys.stdin.readline
read = sys.stdin.read

#n,m,*d= [int(i) for i in read().split()]

#a,t,k = [int(i) for i in readline().split()]

n,x,*a = [int(i) for i in read().split()]

r = [0]*n
l = [0]*n
r[-1] = n-1
pt = 0
res = -a[0]
for i in range(n-1):
    while pt < n and res+a[pt] <= n:
        res += a[pt]
        pt += 1
    r[i] = pt
    res -= a[i]

pt = n-1
res = -a[n-1]
for i in range(n-1,0,-1):
    while pt >= 0 and res+a[pt] <= n:
        res += a[pt]
        pt -= 1
    l[i] = pt+1
    res -= a[i-1]


dp = [[0]*n for _ in range(n)]
for i in range(n):
    dp[i][i] = -1


#for i in dp: print(*i)

for j in range(1,n):
    for k in range(l[j],j):
        dp[k][j] = 1

#for i in dp: print(*i)
#print(l,r)
for i in range(n-2,-1,-1):
    j = i
    while j < n:
        if dp[i][j] == 0:
            dp[i][j] = -1
            for k in range(l[i],i):
                dp[k][j] = 1
            dp[i][j+1:r[j]] = [1]*(r[j]-(j+1))
            j = r[i]
        else:
            j += 1
    #print(dp)


a = dp[0][-1]

if a == 1:
    print("A")
else:
    print("B")