#include "bits/stdc++.h"
#define ll long long
using namespace std;
ll n, a[105];
ll dp[3][3][105];

// last day done (gym isg = 1) contest (isc = 1) else 0;

ll f(ll isg, ll isc, ll day){
    if(day == n) return 0;
    if(dp[isg][isc][day] != -1) return dp[isg][isc][day];
    if(a[day] == 0){
        return dp[isg][isc][day] = 1 + f(0, 0, day+1);
    }
    else if(a[day] == 1){
        if(isc == 0) return dp[isg][isc][day] = min(f(0, 1, day+1), 1 + f(0, 0, day+1));
        else return dp[isg][isc][day] = 1 + f(0, 0, day+1);
    }
    else if(a[day] == 2){
        if(isg == 0) return dp[isg][isc][day] = min(f(1, 0, day+1), 1 + f(0, 0, day+1));
        else return dp[isg][isc][day] = 1 + f(0, 0, day+1);
    }
    else if(a[day] == 3){
        if(!isg && !isc) return dp[isg][isc][day] = min(f(1, 0, day+1),  f(0, 1, day+1));
        else if(!isg) return dp[isg][isc][day] = min(f(1, 0, day+1), 1 + f(0, 0, day+1));
        else return dp[isg][isc][day] = min(f(0, 1, day+1), 1 + f(0, 0, day+1));
    }
}

int main(){
    cin >> n;
    memset(dp, -1, sizeof dp);
    for(int i = 0; i < n; i++) cin >> a[i];
    cout << f(0, 0, 0);
    return 0;
}