#include <iostream>#include <cstdio>#include <cstdlib>#include <cstring>using namespace std;#define maxn 30005int n;int cow[maxn];int f[maxn][5];void input(){ scanf("%d", &n); for (int i = 1; i <= n; i++) scanf("%d", &cow[i]);}void work(){ memset(f, 0, sizeof(f)); for (int i = 1; i <= n; i++) { for (int j = 1; j <= 3; j++) { f[i][j] = f[i - 1][1]; for (int k = 2; k <= j; k++) f[i][j] = min(f[i][j], f[i - 1][k]); if (cow[i] != j) f[i][j]++; } } int ans = n; for (int i = 1; i <= 3; i++) ans = min(ans, f[n][i]); for (int i = 1; i <= n; i++) { for (int j = 1; j <= 3; j++) { f[i][j] = f[i - 1][3]; for (int k = 2; k >= j; k--) f[i][j] = min(f[i][j], f[i - 1][k]); if (cow[i] != j) f[i][j]++; } } for (int i = 1; i <= 3; i++) ans = min(ans, f[n][i]); printf("%dn", ans);}int main(){ input(); work(); return 0;}
