#include <bits/stdc++.h>

#define File(a) freopen(a ".in", "r", stdin), freopen(a ".out", "w", stdout)

const int N = 200005;

int f(int a, int b, int c);

int a[2][N];
int n;

int main() {
  scanf("%d", &n);
  for (int i = 1; i <= 2 * n + 1; ++i) scanf("%d", a[0] + i);
  for (int i = 1; i <= 2 * n - 1; ++i) a[1][i] = f(a[0][i], a[0][i + 1], a[0][i + 2]);
  bool flag = true;
  for (int i = 1; i <= 2 * n - 1; ++i) {
    if (i & 1) {
      flag &= a[1][i];
      if (i > 2) flag &= (a[1][i] == a[1][i - 2]);
    } else {
      flag &= !a[1][i];
    }
  }
  if (flag)
    printf("%d\n", a[1][2 * n - 1]);
  else
    puts("0");
  return 0;
}

int f(int a, int b, int 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;
}