B - Vacations(动态规划)

Vasya has n days of vacations! So he decided to improve his IT skills and do sport. Vasya knows the following information about each of thisn days: whether that gym opened and
whether a contest was carried out in the Internet on that day. For thei-th day there are four options:

on this day the gym is closed and the contest is not carried out;
on this day the gym is closed and the contest is carried out;
on this day the gym is open and the contest is not carried out;
on this day the gym is open and the contest is carried out.
On each of days Vasya can either have a rest or write the contest (if it is carried out on this day), or do sport (if the gym is open on this day).

Find the minimum number of days on which Vasya will have a rest (it means, he will not do sport and write the contest at the same time). The only limitation that Vasya has —he does not want to do the same activity on two consecutive
days: it means, he will not do sport on two consecutive days, and write the contest on two consecutive days.

Input

The first line contains a positive integer n (1 ≤ n ≤ 100) — the number of days of Vasya's vacations.

The second line contains the sequence of integers a1, a2, ..., an (0 ≤ ai ≤ 3)
separated by space, where:

ai equals 0, if on thei-th day of vacations the gym is closed and the contest is not carried out;
ai equals 1, if on thei-th day of vacations the gym is closed, but the contest is carried out;
ai equals 2, if on thei-th day of vacations the gym is open and the contest is not carried out;
ai equals 3, if on thei-th day of vacations the gym is open and the contest is carried out.

Output

Print the minimum possible number of days on which Vasya will have a rest. Remember that Vasya refuses:

to do sport on any two consecutive days,
to write the contest on any two consecutive days.

Example

Input

4
1 3 2 0

Output

2

Input

7
1 3 3 2 1 2 3

Output

0

Input

22 2

Output

1

Note

In the first test Vasya can write the contest on the day number 1 and do sport on the day number 3. Thus, he will have a rest for only 2 days.

In the second test Vasya should write contests on days number 1, 3, 5 and 7, in other days do sport. Thus, he will not have a rest for a single day.

In the third test Vasya can do sport either on a day number 1 or number 2. He can not do sport in two days, because it will be contrary to the his limitation. Thus, he will have a rest for only one day.

题目大体的意思就是说：在给出的n天中 0表示比赛和运动都没有 1 表示只有比赛 2表示只有运动 3表示比赛运动都有

然后求得是最小的休息时间    有一个要求就是两天之间 不重复做同一件事情这是被要求的

然后就是题目的思路 我是转载的转载如下

转载来自：http://blog.csdn.net/cmershen/article/details/52006524

然后想写是想理清楚自己的对他的理解

dp[i][0]=min(dp[i-1][0],dp[i-1][1],dp[i-1][2])+1;//表示如果这一天什么都不干也就是休息的话那么休息的天数就是前面干某一件事情之后的天数最小 然后+1
if(num[i]==1||num[i]==3)
dp[i][1]=min(dp[i-1][2],dp[i-1][0]);

//这个表示的是说如果这一天干了比赛这件事情的话 那么前一天就必须是休息或者是运动了 这样子就符合了 然后从中选择最小的

if(num[i]==2||num[i]==3)
dp[i][2]=min(dp[i-1][1],dp[i-1][0]);

//这个表示的是如果这一天做运动这件事情的话 那么前一天也必须是比赛或则是休息只有这样子才是符合的然后从中间选择最小的 就是这个样子
至于两个地方都有dp[i][3] 是因为你不知道这一天要做哪个所以你就都弄
到最后在选择最小的那个

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
int INF=0X3f3f3f3f;
int min(int a,int b,int c)
{
int m=a;
if(b<a)m=b;
if(c<a)m=c;
return m;
}
int main()
{
int n;
int dp[111][3];
int num[111];
scanf("%d",&n);
for(int i=1;i<=n;i++)
scanf("%d",&num[i]);
memset(dp,INF,sizeof(dp));
dp[0][0]=0;
for(int i=1;i<=n;i++)
{
dp[i][0]=min(dp[i-1][0],dp[i-1][1],dp[i-1][2])+1;
if(num[i]==1||num[i]==3)
dp[i][1]=min(dp[i-1][2],dp[i-1][0]);
if(num[i]==2||num[i]==3)
dp[i][2]=min(dp[i-1][1],dp[i-1][0]);
}
printf("%d\n",min(dp
[0],dp
[1],dp
[2]));
return 0;
}