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#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define mod 1000000007
#define f first
#define s second
#define si(x)   scanf("%d",&x)
#define sl(x)   scanf("%I64d",&x)
#define CLR(x)  memset(x,0,sizeof(x))
#define RESET(x,a) memset(x,a,sizeof(x))
#define pi pair<int,int>
#define pb push_back
#define mp make_pair
#define debug(x) cerr<<">value ("<<#x<<") : "<<x<<endl;

int dp[3][200];
int a[200];
int INF=10000;

int main()
{
//    ios_base::sync_with_stdio(false);
//    cin.tie(NULL);
    int t,n,m,i,j;
    si(n);
    for(i=0;i<n;i++)
    {
        si(a[i]);
        dp[0][i]=dp[1][i]=dp[2][i]=INF;
    }
    dp[0][i]=dp[1][i]=dp[2][i]=INF;
    dp[0][0]=0;
    for(i=0;i<n;i++)
    {
        dp[0][i+1] = min( min(dp[0][i],dp[1][i]) , dp[2][i] );
        dp[0][i+1]++;
        if(a[i]==1)
        {
            dp[1][i+1] = min(dp[0][i], dp[2][i] );
        }
        else if(a[i]==2)
        {
            dp[2][i+1] = min(dp[0][i], dp[1][i] );
        }
        else if(a[i]==3)
        {
            dp[1][i+1] = min(dp[0][i], dp[2][i] );
            dp[2][i+1] = min(dp[0][i], dp[1][i] );
        }
    }
    i=n;
    int ans= min( min(dp[0][i],dp[1][i]) , dp[2][i] );
    printf("%d\n",ans);
    return 0;
}