#include <bits/stdc++.h>
using namespace std;
int n, a, b, sum;
int main() {
  cin >> n;
  b = -1;
  sum = 0;
  for (int i = 0; i < n; i++) {
    cin >> a;
    if (a == 0 || (a == b && b != 3)) {
      sum++;
      b = 0;
    } else if (a == 3 && b == 1)
      b = 2;
    else if (a == 3 && b == 2)
      b = 1;
    else
      b = a;
  }
  cout << sum << endl;
  return 0;
}
