# 想定解 def solve(N, As): assert len(As) == 2 * N + 1 def LeviCivitaSymbol(i, j, k): if (i, j, k) in ((0, 1, 2), (1, 2, 0), (2, 0, 1)): return 1 elif (i, j, k) in ((2, 1, 0), (1, 0, 2), (0, 2, 1)): return 2 else: return 0 As = [LeviCivitaSymbol(As[i], As[i + 1], As[i + 2]) for i in range(len(As) - 2)] As.reverse() ans_one = ([1, 0, 2, 0] * ((len(As) + 3) // 4))[:len(As)] ans_two = ([2, 0, 1, 0] * ((len(As) + 3) // 4))[:len(As)] if As == ans_one: return 1 elif As == ans_two: return 2 else: return 0 def slow(N, As): assert len(As) == 2 * N + 1 def LeviCivitaSymbol(i, j, k): if (i, j, k) in ((0, 1, 2), (1, 2, 0), (2, 0, 1)): return 1 elif (i, j, k) in ((2, 1, 0), (1, 0, 2), (0, 2, 1)): return 2 else: return 0 for _ in range(N): As = [LeviCivitaSymbol(As[i], As[i + 1], As[i + 2]) for i in range(len(As) - 2)] assert len(As) == 1 return As[0] def test1(t): import random for _ in range(t): N = random.randint(1, 100) As = [random.randint(0, 2) for _ in range(2 * N + 1)] ans_slow = slow(N, As.copy()) ans_solve = solve(N, As.copy()) # print(ans_slow, ans_solve, As) assert ans_slow == ans_solve print("test1 passed") def test2(Nmax): from itertools import permutations for N in range(1, Nmax + 1): for As in permutations(range(3), 2 * N + 1): As = list(As) ans_slow = slow(N, As.copy()) ans_solve = solve(N, As.copy()) # print(ans_slow, ans_solve, As) assert ans_slow == ans_solve print("test2 passed") def main(): #""" N = int(input()) As = list(map(int, input().split())) """ import random N = 5 * 10 ** 5 As = [random.randint(0, 2) for _ in range(2 * N + 1)] #""" print(solve(N, As)) main()