【Educational Codeforces Round 33 A】Chess For Three

【链接】 我是链接,点我呀:)
【题意】

在这里输入题意

【题解】

模拟题.知道哪个人是旁观者就好

【代码】

/*
  	1.Shoud it use long long ?
  	2.Have you ever test several sample(at least therr) yourself?
  	3.Can you promise that the solution is right? At least,the main ideal
  	4.use the puts("") or putchar() or printf and such things?
  	5.init the used array or any value?
  	6.use error MAX_VALUE?
  	7.use scanf instead of cin/cout?
*/
#include <bits/stdc++.h>
using namespace std;

int n,x,now;

int main(){
	#ifdef LOCAL_DEFINE
	    freopen("F:\c++source\rush_in.txt", "r", stdin);
	#endif
	ios::sync_with_stdio(0),cin.tie(0);
	cin >> n;
	now = 3;
	for (int i =1;i <= n;i++){
	    cin >> x;
	    if (x==now) return cout <<"NO"<<endl,0;
	    for (int j = 1;j <= 3;j++)
	    	if (j!=x && j!=now){
	    	 	now = j;
	    	 	break;
	    	}
	}	
	cout <<"YES"<<endl;
	return 0;
}