#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
using ll = long long;
constexpr int INF = 0x3f3f3f3f;
constexpr long long LINF = 0x3f3f3f3f3f3f3f3fLL;
constexpr double EPS = 1e-8;
constexpr int MOD = 1000000007;
// constexpr int MOD = 998244353;
constexpr int DY[]{1, 0, -1, 0}, DX[]{0, -1, 0, 1};
constexpr int DY8[]{1, 1, 0, -1, -1, -1, 0, 1}, DX8[]{0, -1, -1, -1, 0, 1, 1, 1};
template <typename T, typename U> inline bool chmax(T &a, U b) { return a < b ? (a = b, true) : false; }
template <typename T, typename U> inline bool chmin(T &a, U b) { return a > b ? (a = b, true) : false; }
struct IOSetup {
  IOSetup() {
    std::cin.tie(nullptr);
    std::ios_base::sync_with_stdio(false);
    std::cout << fixed << setprecision(20);
  }
} iosetup;

int main() {
  int n; cin >> n;
  vector<int> a(n * 2 + 1); REP(i, n * 2 + 1) cin >> a[i];
  FOR(i, 1, n * 2 + 1) {
    if (a[i - 1] == a[i]) {
      cout << 0 << '\n';
      return 0;
    }
  }
  for (int i = 3; i < n * 2 + 1; i += 2) {
    if (a[i - 2] != a[i]) {
      cout << 0 << '\n';
      return 0;
    }
  }
  if (a[0] == a[2]) {
    cout << 0 << '\n';
    return 0;
  }
  vector<int> b;
  for (int i = 0; i + 2 < n * 2 + 1; ++i) {
    if (a[i] == 0 && a[i + 1] == 1 && a[i + 2] == 2 ||
        a[i] == 1 && a[i + 1] == 2 && a[i + 2] == 0 ||
        a[i] == 2 && a[i + 1] == 0 && a[i + 2] == 1) {
      b.emplace_back(1);
    } else if (a[i] == 2 && a[i + 1] == 1 && a[i + 2] == 0 ||
                a[i] == 1 && a[i + 1] == 0 && a[i + 2] == 2 ||
                a[i] == 0 && a[i + 1] == 2 && a[i + 2] == 1) {
      b.emplace_back(2);
    } else {
      b.emplace_back(0);
    }
  }
  cout << b.back() << '\n';
  return 0;
}