vacations

#include <iostream>
#include <vector>
#include <map>

using namespace std;

#define ll long long
#define cy cout << "YES"
#define cn cout << "NO"
#define nl "\n"
#define fi first
#define se second
#define cin(v) for (int i = 0; i < n, cin >> v[i]; i++)
#define cout(v) for (int i = 0; i < v.size(), cout << v[i] << " "; i++)
#define all(v) v.begin(), v.end()
#define sz(s) s.size()

void sherry()
{
    ios_base::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
#ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin), freopen("output.txt", "w", stdout);
#endif
}
ll n;
vector<ll> a;
vector<vector<int>> dp;
int rec(int idx, int prev)
{
    if (idx == n)
        return 0;
    int &ret = dp[idx][prev];
    if (~ret)
        return ret;
    ret = 1e9;
    if (a[idx] == 0)
        return ret = 1 + rec(idx + 1, a[idx]);
    if (a[idx] == 1 || a[idx] == 2)
        return ret = (a[idx] == prev) + rec(idx + 1, (a[idx] == prev ? 0 : a[idx]));
    if (a[idx] == 3)
    {
        if (prev == 1)
            ret = min(ret, rec(idx + 1, 2));
        else if (prev == 2)
            ret = min(ret, rec(idx + 1, 1));
        else
            ret = min({ret, rec(idx + 1, 1), rec(idx + 1, 2)});
    }
    return ret;
}
void solve()
{
    cin >> n;
    a.resize(n);
    cin(a);
    dp.assign(n, vector<int>(4, -1));
    cout << rec(0, 0);
}
int main()
{
    sherry();
    int t = 1;
    // cin >> t;
    while (t--)
        solve();
    return 0;
}