public static void main(String[] args) {

Scanner sc = new Scanner(System.in);

int n = sc.nextInt(), ret = 0;

int[] arr = new int[n];

// dp0: rest dp1: go to gym, dp2: go to contest

int[] dp0 = new int[n + 1], dp1 = new int[n + 1], dp2 = new int[n + 1];

for (int i = 0; i < n; i++) {

int a = sc.nextInt();

arr[i] = a;

}

for (int i = 0; i < n; i++) {

dp0[i + 1] = Math.max(dp0[i], Math.max(dp1[i], dp2[i]));

if (arr[i] == 1) { // contest

dp2[i + 1] = Math.max(dp0[i] + 1, Math.max(dp1[i] + 1, dp2[i]));

} else if (arr[i] == 2) { // gym

dp1[i + 1] = Math.max(dp0[i] + 1, Math.max(dp2[i] + 1, dp1[i]));

} else if (arr[i] == 3) { // either

dp1[i + 1] = Math.max(dp0[i] + 1, Math.max(dp2[i] + 1, dp1[i]));

dp2[i + 1] = Math.max(dp0[i] + 1, Math.max(dp1[i] + 1, dp2[i]));

}

}

System.out.println(n - Math.max(dp0[n], Math.max(dp1[n], dp2[n])));

}