programm

#define _CRT_SECURE_NO_DEPRECATE
#include<iostream>
#include<string>
#include<conio.h>
#include<vector>
#include<algorithm>

using namespace std;

int main() {
//	freopen("out.txt", "wt", stdout); freopen("in.txt", "rt", stdin);
	vector<vector<int>> a;
	a.resize(3);
	bool contest = true;
	bool sport = true;
	int n;
	int g;

	cin >> n;
	cin >> g;
	a[0].push_back(0);
	if (g == 0) {
		a[1].push_back(0);
		a[2].push_back(0);
	}
	if (g == 1) {
		a[1].push_back(1);
		a[2].push_back(0);
		contest = false;
	}
	if (g == 2) {
		a[1].push_back(0);
		a[2].push_back(1);
		sport = false;
	}
	if (g == 3) {
		a[1].push_back(1);
		a[2].push_back(1);
		contest = false;
		sport = false;
	}
	for (int i = 1; i < n; i++) {
		cin >> g;
		if (g == 0) {
			a[0].push_back(max(a[0][i - 1], max(a[1][i - 1], a[2][i - 1])));
			a[1].push_back(max(a[0][i - 1], max(a[1][i - 1], a[2][i - 1])));
			a[2].push_back(max(a[0][i - 1], max(a[1][i - 1], a[2][i - 1])));
			contest = true;
			sport = true;
		}


		if (g == 1) {
			a[0].push_back(max(a[0][i - 1], max(a[1][i - 1], a[2][i - 1])));
			if (contest == true) {
				a[1].push_back(max(a[0][i - 1], max(a[1][i - 1], a[2][i - 1]))+1);
				contest = false;
			}
			else {
				a[1].push_back(max(a[0][i - 1], max(a[1][i - 1], a[2][i - 1])));
				contest = true;
			}
			a[2].push_back(max(a[0][i - 1], max(a[1][i - 1], a[2][i - 1])));
			sport = true;
		}


		if (g == 2) {
			a[0].push_back(max(a[0][i - 1], max(a[1][i - 1], a[2][i - 1])));
			a[1].push_back(max(a[0][i - 1], max(a[1][i - 1], a[2][i - 1])));
			if (sport == true) {
				a[2].push_back(max(a[0][i - 1], max(a[1][i - 1], a[2][i - 1])) + 1);
				sport = false;
			}
			else {
				a[2].push_back(max(a[0][i - 1], max(a[1][i - 1], a[2][i - 1])));
				sport = true;
			}
			contest = true;
		}


		if (g == 3) {
			a[0].push_back(max(a[0][i - 1], max(a[1][i - 1], a[2][i - 1])));
			if (contest == true) {
				a[1].push_back(max(a[0][i - 1], max(a[1][i - 1], a[2][i - 1])) + 1);
				contest = false;
			}
			else {
				a[1].push_back(max(a[0][i - 1], max(a[1][i - 1], a[2][i - 1])));
				contest = true;
			}
			if (sport == true) {
				a[2].push_back(max(a[0][i - 1], max(a[1][i - 1], a[2][i - 1])) + 1);
				sport = false;
			}
			else {
				a[2].push_back(max(a[0][i - 1], max(a[1][i - 1], a[2][i - 1])));
				sport = true;
			}
		}
	}


	int k = (n - max(a[0][n - 1], max(a[1][n - 1], a[2][n - 1])));
	cout << k;
	return 0;
}