N = int(input())
A = list(map(int, input().split()))
B = [0] * (2 * N - 1)
for i in range(2 * N - 1):
    if (A[i + 2] - A[i + 1]) % 3 == 1 and (A[i + 1] - A[i]) % 3 == 1:
        B[i] = 1
    elif (A[i + 2] - A[i + 1]) % 3 == 2 and (A[i + 1] - A[i]) % 3 == 2:
        B[i] = 2
    else:
        B[i] = 0
if B[0] == 0:
    print(0)
    exit()
if N & 1:
    ans = B[0]
else:
    ans = B[2]

for i in range(2 * N - 1):
    if i & 3 == 2:
        if B[i] != B[2]:
            print(0)
            exit()
    elif i & 3 == 0:
        if B[i] != B[0]:
            print(0)
            exit()
    else:
        if B[i] != 0:
            print(0)
            exit()
print(ans)