99
1
3
2
2
3
1
1
3
3
3
3
3
3
1
1
3
3
3
3
1
1
3
2
1
1
1
1
1
1
1
3
2
2
2
1
3
3
1
1
3
2
1
3
3
1
2
3
3
3
1
2
2
2
3
3
3
3
3
3
2
2
2
2
3
3
3
1
1
3
2
1
1
2
2
2
3
3
2
1
1
2
2
1
3
2
1
1
2
3
3
3
3
2
2
2
2
2
1
3
 1
3
 2
2
1
 5
2
3
3
1
1
 5
2
2
2
2
2
 6
2
2
2
3
1
3
 5
2
3
3
3
3
 1
2
 100
2
2
1
3
1
3
3
1
1
3
1
1
3
2
1
3
1
1
3
3
2
2
3
1
1
2
3
2
2
3
1
1
2
3
2
1
2
2
3
3
1
1
3
1
2
1
3
1
1
3
2
2
2
1
1
1
3
1
3
2
1
2
2
2
3
3
2
1
1
3
3
2
1
2
1
1
3
1
2
3
2
3
3
3
2
2
1
3
1
2
3
1
2
3
3
1
2
1
3
1
 4
1
2
2
1
 3
3
3
1
 8
1
1
1
1
1
1
1
1
 5
1
1
1
1
3
 3
2
2
3
 3
2
2
2
 2
2
2
 4
2
3
3
3
 2
3
2
 100
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
 7
2
2
2
2
2
2
2
 3
2
1
1
 10
2
3
3
3
3
2
2
2
3
2
 3
3
1
3
 2
3
1
 3
1
2
3
 42
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
 2
1
3
 100
2
3
1
2
3
3
3
1
1
1
1
3
3
3
3
1
2
3
3
3
3
3
3
3
1
2
2
2
3
1
1
3
3
3
3
3
3
3
3
1
2
3
3
3
1
1
1
1
3
3
3
3
1
2
3
1
2
2
2
3
3
2
1
3
3
1
2
3
1
1
1
2
2
2
3
1
1
1
1
1
1
3
2
2
2
2
2
2
3
1
2
2
2
2
2
3
3
2
1
1
 3
3
2
2
 3
3
2
3
 2
3
3
 3
2
2
1
 5
1
1
2
2
3
 3
1
3
1
 3
1
1
3

YES
 NO
 NO
 NO
 YES
 NO
 YES
 YES
 NO
 NO
 NO
 YES
 NO
 NO
 YES
 YES
 YES
 NO
 YES
 YES
 NO
 NO
 NO
 NO
 NO
 YES
 YES
 YES
 NO
 NO
 NO
 YES
 NO
 NO
 NO

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.*;

import java.util.Scanner;

public class Main {
    private static FastReader scanner = new FastReader();
    public static void main(String[] args) {
        int n = scanner.nextInt();
        int ck = 3;
        for(int i = 0 ; i<n;i++){
            int k = scanner.nextInt();
            if(k==ck){
                System.out.println("NO");
                return;
            }
            ck = 6-ck-k;
        }
        System.out.println("YES");
    }
    private static void swap(int[] array , int a ,int b){
        if (a==b){
            return;
        }
        int temp = array[a];
        array[a] =array[b];
        array[b] =temp;
    }
    private static String revString(String str){
        StringBuilder sb = new StringBuilder(str);
        sb.reverse();
        return sb.toString();
    }
    private static int fibo(int n){
        int[] dp = new int[n];
        for(int i= 0 ;i<n;i++){
            if(i<2){
                dp[i] = 1;
            }else{
                dp[i] =dp[i-1]+dp[i-2];
            }
        }
        return dp[dp.length-1];
    }
    private static void swap(char[] array , int a,int b){
        if(a==b){
            return;
        }
        char temp = array[a];
        array[a] = array[b];
        array[b] = temp;
    }
    private static Scanner slowscanner = new Scanner(System.in);
    private static int max(int[] array ){
        int min = Integer.MIN_VALUE;
        for(int i = 0;i< array.length;i++){
            if(array[i]>min){
                min = array[i];
            }
        }
        return min;
    }
    private static int min(int[] array ){
        int min = Integer.MAX_VALUE;
        for(int i = 0;i< array.length;i++){
            if(array[i]<min){
                min = array[i];
            }
        }
        return min;
    }
    private static void readArray(int[] array){
        for(int i = 0;i< array.length;i++){
            array[i] = scanner.nextInt();
        }
    }
    private static int gcd(int a , int b){
        if(b==0) return  a;
        else return gcd(b,a%b);
    }
    private static long fact(int n){
        if(n==1 || n==0) return 1;
        else return (long) n*fact(n-1);
    }
    private static int Arraysum(int[] array){
        int sum = 0;
        for(int i = 0 ;i< array.length;i++){
            sum+=array[i];
        }
        return sum;
    }
    private static boolean isPrime(long n){
        if(n==1){
            return false;
        }
        for(long i = 2;i<=Math.sqrt(n);i++){
            if(n%i==0){
                return false;
            }
        }
        return true;
    }
    private static int multiply(int[] array){
        int mult = 1 ;
        for(int i = 0 ;i< array.length;i++) {
            mult *= array[i];
        }
        return mult;
    }
    private static int FromStringtoInt(String s){
        s = s.replaceAll("[^0-9]","");
        return Integer.parseInt(s);
    }
    static class BIT{
        static int[] BitTree = new int[1000];
        int sum(int index){
            int s =0;
//            index+=1;
            while (index>0){
                s+=BitTree[index];
                index-=(index&-index);
            }
            return s;
        }
        public static void updateBIT(int n, int index, int val) {
            index = index + 1;
            while(index <= n) {
                BitTree[index] += val;
                index += index & (-index);
            }
        }
        void constructBITree(int arr[], int n) {
            for(int i=1; i<=n; i++)
                BitTree[i] = 0;
            for(int i = 0; i < n; i++)
                updateBIT(n, i, arr[i]);
        }
    }
    static class FastReader {
        BufferedReader br;
        StringTokenizer st;

        public FastReader()
        {
            br = new BufferedReader(new
                    InputStreamReader(System.in));
        }

        String next()
        {
            while (st == null || !st.hasMoreElements())
            {
                try
                {
                    st = new StringTokenizer(br.readLine());
                }
                catch (IOException  e)
                {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt()
        {
            return Integer.parseInt(next());
        }

        long nextLong()
        {
            return Long.parseLong(next());
        }

        double nextDouble()
        {
            return Double.parseDouble(next());
        }

        String nextLine()
        {
            String str = "";
            try
            {
                str = br.readLine();
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
            return str;
        }
    }

}