#include <bits/stdc++.h>
using namespace std;
int dp[101][2];
int main() {
  ios_base::sync_with_stdio(NULL);
  cin.tie(NULL);
  cout.tie(NULL);
  ;
  int n;
  cin >> n;
  vector<int> v(n);
  for (int i = 0; i < n; i++) cin >> v[i];
  if (v[0] == 1) dp[0][0] = 0, dp[0][1] = 1;
  if (v[0] == 2) dp[0][0] = 1, dp[0][1] = 0;
  if (v[0] == 3) dp[0][0] = 1, dp[0][1] = 1;
  for (int i = 1; i < n; i++) {
    if (v[i] == 0) {
      dp[i][0] = max(dp[i - 1][0], dp[i - 1][1]);
      dp[i][1] = dp[i][0];
    }
    if (v[i] == 1) {
      dp[i][0] = max(dp[i - 1][0], dp[i - 1][1]);
      dp[i][1] = dp[i - 1][0] + 1;
    }
    if (v[i] == 2) {
      dp[i][0] = dp[i - 1][1] + 1;
      dp[i][1] = max(dp[i - 1][0], dp[i - 1][1]);
    }
    if (v[i] == 3) {
      dp[i][0] = dp[i - 1][1] + 1;
      dp[i][1] = dp[i - 1][0] + 1;
    }
  }
  cout << n - max(dp[n - 1][0], dp[n - 1][1]);
  return 0;
}
