n=int(input())
a=list(map(int,input().split()))
m=max(a)
ind=[]
for i in range(20,n-20):
    if all(a[i]>=a[i+j] for j in range(-5,6)):
        ind.append(i)


dt=0
for i in range(len(ind)-1):
    dt=max(dt,ind[i+1]-ind[i])

ans=n/dt
if 255<ans<265:
    print("C4")
elif 290<ans<300:
    print("D4")
elif 322<ans<332:
    print("E4")
elif 344<ans<353:
    print("F4")
elif 388<ans<398:
    print("G4")
elif 431<ans<441:
    print("A4")
else:
    print("B4")