#include <bits/stdc++.h>
#include <atcoder/modint>
using namespace std;
using namespace atcoder;
//using mint = modint998244353;
using mint = modint1000000007;
using ll = long long;
using ld = long double;
using pll = pair<ll, ll>;
using tlll = tuple<ll, ll, ll>;
constexpr ll INF = 1LL << 60;
template<class T> bool chmin(T& a, T b) {if (a > b) {a = b; return true;} return false;}
template<class T> bool chmax(T& a, T b) {if (a < b) {a = b; return true;} return false;}
ll safemod(ll A, ll M) {return (A % M + M) % M;}
ll divfloor(ll A, ll B) {if (B < 0) {return divfloor(-A, -B);} return (A - safemod(A, B)) / B;}
ll divceil(ll A, ll B) {if (B < 0) {return divceil(-A, -B);} return divfloor(A + B - 1, B);}
#define FINALANS(A) do {cout << (A) << '\n'; exit(0);} while (false)

ll f(ll a, ll b, ll c)
{
  if (a == 0 && b == 1 && c == 2)
    return 1;
  if (a == 1 && b == 2 && c == 0)
    return 1;
  if (a == 2 && b == 0 && c == 1)
    return 1;
  if (a == 2 && b == 1 && c == 0)
    return 2;
  if (a == 1 && b == 0 && c == 2)
    return 2;
  if (a == 0 && b == 2 && c == 1)
    return 2;
  return 0;
}

int main()
{
  ll N;
  cin >> N;
  vector<ll> A(2 * N + 1);
  for (ll i = 0; i < 2 * N + 1; i++)
  {
    cin >> A.at(i);
  }

  vector<ll> B(2 * N - 1);
  for (ll i = 0; i < 2 * N - 1; i++)
  {
    B.at(i) = f(A.at(i), A.at(i + 1), A.at(i + 2));
  }

  for (ll i = 2 * N - 3; i >= 0; i--)
  {
    if (i % 2 != 0)
    {
      if (B.at(i) != 0)
        FINALANS(0);
    }
    else
    {
      if (i % 4 == (2 * N - 2) % 4)
      {
        if (B.at(i) != B.back())
          FINALANS(0);
      }
      else
      {
        if (B.at(i) == 0 || B.at(i) == B.back())
          FINALANS(0);
      }
    }
  }
  FINALANS(B.back());
}