【CodeForces 698A】Vacations

#include <cstdio>
#include <cstring>
#include <algorithm>
#define N 105
using namespace std;
int n,a,f[N][3],ans;
int main(){
	memset(f,0x3f3f3f3f,sizeof f);
	f[0][0]=0;
	scanf("%d",&n);
	for(int i=1;i<=n;i++){
		scanf("%d",&a);
		f[i][0]=min(f[i-1][0],min(f[i-1][1],f[i-1][2]))+1;
		if(a&&a!=2)f[i][1]=min(f[i-1][0],f[i-1][2]);
		if(a>1)f[i][2]=min(f[i-1][0],f[i-1][1]);
	}
	printf("%d",min(min(f[n][0],f[n][1]),f[n][2]));
}