#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
using namespace std;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int n;
  cin >> n;
  int arr[n + 1];
  int dp[n + 1][3];
  for (int i = 1; i <= n; i++) cin >> arr[i];
  dp[0][0] = dp[0][1] = dp[0][2] = 0;
  for (int i = 1; i <= n; i++) {
    dp[i][0] = max(max(dp[i - 1][1], dp[i - 1][2]), dp[i - 1][0]);
    if (arr[i] == 0) {
      dp[i][1] = dp[i - 1][1];
      dp[i][2] = dp[i - 1][2];
    }
    if (arr[i] == 1) {
      dp[i][1] = max(dp[i - 1][0] + 1, dp[i - 1][2] + 1);
      dp[i][2] = max(dp[i - 1][2], dp[i - 1][0]);
    }
    if (arr[i] == 2) {
      dp[i][2] = max(dp[i - 1][0] + 1, dp[i - 1][1] + 1);
      dp[i][1] = max(dp[i - 1][1], dp[i - 1][0]);
    }
    if (arr[i] == 3) {
      dp[i][1] = max(dp[i - 1][0] + 1, dp[i - 1][2] + 1);
      dp[i][2] = max(dp[i - 1][0] + 1, dp[i - 1][1] + 1);
    }
  }
  cout << n - max(dp[n][0], max(dp[n][1], dp[n][2]));
  return 0;
}
