N = int(input())
As = list(map(int, input().split()))
cnt = 0
while len(As) >= 3 and cnt <= 30:
    cnt += 1
    Bs = [None]*(len(As)-2)
    for i in range(1, len(As)-1):
        if (As[i - 1] == 0 and As[i] == 1 and As[i + 1] == 2):
            Bs[i - 1] = 1
        elif (As[i - 1] == 1 and As[i] == 2 and As[i + 1] == 0):
            Bs[i - 1] = 1
        elif (As[i - 1] == 2 and As[i] == 0 and As[i + 1] == 1):
            Bs[i - 1] = 1
        elif (As[i - 1] == 2 and As[i] == 1 and As[i + 1] == 0):
            Bs[i - 1] = 2
        elif (As[i - 1] == 1 and As[i] == 0 and As[i + 1] == 2):
            Bs[i - 1] = 2
        elif (As[i - 1] == 0 and As[i] == 2 and As[i + 1] == 1):
            Bs[i - 1] = 2
        else:
            Bs[i - 1] = 0
    As = Bs
    # print(As)

if (len(As) == 1):
    print(As[0])
    exit()

if all(i == 0 for i in As[1::2]):
    if all(i == 2 for i in As[::4]) and all(i == 1 for i in As[2::4]) and len(As) % 4 == 3:
        print(1)
    elif all(i == 1 for i in As[::4]) and all(i == 2 for i in As[2::4]) and len(As) % 4 == 1:
        print(1)
    elif all(i == 2 for i in As[::4]) and all(i == 1 for i in As[2::4]) and len(As) % 4 == 1:
        print(2)
    elif all(i == 1 for i in As[::4]) and all(i == 2 for i in As[2::4]) and len(As) % 4 == 3:
        print(2)
    else:
        print(0)
else:
    print(0)