#include <bits/stdc++.h>
using namespace std;
typedef int* Pint;
typedef long long* PLL;
const int MAXN = 1E4;
int a[110], f[110][3]{};
int n;
int main() {
  scanf("%d", &n);
  for (int i = 1; i <= n; i++) scanf("%d", a + i);
  for (int i = 1; i <= n; i++) {
    f[i][0] = min(min(f[i - 1][0], f[i - 1][1]), f[i - 1][2]) + 1;
    f[i][1] = f[i][2] = MAXN;
    if (a[i] & 1) f[i][1] = min(f[i - 1][0], f[i - 1][2]);
    if (a[i] & 2) f[i][2] = min(f[i - 1][0], f[i - 1][1]);
  }
  printf("%d\n", min(min(f[n][0], f[n][1]), f[n][2]));
}
