#include<bits/stdc++.h>
using namespace std;
long long a[1000000];
long long dp[100000][1000];
int main() {
long long n;
cin>>n;
for (int i=1;i<=n;i++) {
cin>>a[i];
}
for (int i=1;i<=n;i++) {
dp[i][0] = max(dp[i-1][0],max(dp[i-1][1],max(dp[i][0],dp[i-1][2])));
if (a[i] == 1 || a[i] == 3) {
dp[i][1] = max(dp[i-1][0],dp[i-1][2]) + 1;
}
if (a[i] == 2 || a[i] == 3) {
dp[i][2] = max(dp[i-1][0],dp[i-1][1]) + 1;
}
}
cout<<n - max(dp[n][0],max(dp[n][1],dp[n][2]));
return 0;
}
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