#include <bits/stdc++.h>
using namespace std;
const double eps = 1e-9;
const long long MOD = 998244353;
const long long N = (long long)1e4 + 9;
const long long inf = 1 << 30;
template <class T>
T gcd(T a, T b) {
  return (b != 0 ? gcd<T>(b, a % b) : a);
}
template <class T>
T lcm(T a, T b) {
  return (a / gcd<T>(a, b) * b);
}
template <typename T>
T exp(T b, T p) {
  T x = 1;
  while (p) {
    if (p & 1) x = (x * b);
    b = (b * b);
    p = p >> 1;
  }
  return x;
}
inline long long ones(long long n) {
  long long res = 0;
  while (n && ++res) n -= n & (-n);
  return res;
}
inline bool EQ(double a, double b) { return fabs(a - b) < 1e-9; }
long long mem[109][3];
long long n, arr[109];
long long go(long long idx, long long last) {
  if (idx == n) return 0;
  long long &ret = mem[idx][last];
  if (ret != -1) return ret;
  ret = -inf;
  if (arr[idx] == 0) ret = go(idx + 1, 0);
  if (arr[idx] == 3) {
    if (last != 1) ret = max(ret, 1 + go(idx + 1, 1));
    if (last != 2) ret = max(ret, 1 + go(idx + 1, 2));
  }
  if (arr[idx] == 1) {
    if (last != 1)
      ret = 1 + go(idx + 1, 1);
    else
      ret = go(idx + 1, 0);
  }
  if (arr[idx] == 2) {
    if (last != 2)
      ret = 1 + go(idx + 1, 2);
    else
      ret = go(idx + 1, 0);
  }
  return ret;
}
int32_t main() {
  ios::sync_with_stdio(0);
  cin.tie(nullptr);
  cout.tie(0);
  cin >> n;
  for (long long i = 0; i < n; ++i) {
    cin >> arr[i];
  }
  memset(mem, -1, sizeof(mem));
  long long ans = go(0, 0);
  cout << n - ans;
}
