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.util.*;

public class Check2 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int t=sc.nextInt();
        int[] ar=new int[t];
        for(int i=0;i<t;i++){
           ar[i]=sc.nextInt();
        }
        int spectator=3;
        int op1=1;
        int op2=2;
        boolean ans=true;
        for(int i=0;i<t;i++){
            if(ar[i]!=spectator){
                if(ar[i]==op1){
                    int temp=op2;
                    op2=spectator;
                    spectator=temp;
                }else {
                    int temp=op1;
                    op1=spectator;
                    spectator=temp;
                }
            }else {
                ans=false;
                break;
            }
        }
        if(ans){
            System.out.println("YES");
        }else {
            System.out.println("NO");
        }







    }



    public static long power(long a, long b, long c) {
        long ans = 1;
        while (b != 0) {
            if (b % 2 == 1) {
                ans = ans * a;
                ans %= c;
            }
            a = a * a;
            a %= c;
            b /= 2;
        }
        return ans;
    }

    public static long power1(long a, long b, long c) {
        long ans = 1;
        while (b != 0) {
            if (b % 2 == 1) {
                ans = multiply(ans, a, c);
            }
            a = multiply(a, a, c);
            b /= 2;

        }
        return ans;

    }

    public static long multiply(long a, long b, long c) {
        long res = 0;
        a %= c;
        while (b > 0) {
            if (b % 2 == 1) {
                res = (res + a) % c;
            }
            a = (a + a) % c;
            b /= 2;
        }

        return res % c;

    }

    public static long totient(long n) {
        long result = n;
        for (long i = 2; i * i <= n; i++) {
            if (n % i == 0) {
                //sum=sum+2*i;
                while (n % i == 0) {
                    n /= i;
                    // sum=sum+n;
                }
                result -= result / i;

            }
        }
        if (n > 1) {
            result -= result / n;

        }
        return result;
    }


    public static long gcd(long a, long b) {
        if (b == 0) {
            return a;
        } else {
            return gcd(b, a % b);
        }
    }

    public static boolean[] primes(int n) {
        boolean[] p = new boolean[n + 1];
        p[0] = false;
        p[1] = false;
        for (int i = 2; i <= n; i++) {
            p[i] = true;
        }

        for (int i = 2; i * i <= n; i++) {
            if (p[i]) {
                for (int j = i * i; j <= n; j += i) {
                    p[j] = false;
                }
            }

        }
        return p;
    }

    static int val(char c) {
        if (c >= '0' && c <= '9')
            return (int) c - '0';
        else
            return (int) c - 'A' + 10;
    }

    // Function to convert a
// number from given base
// 'b' to decimal
    static int toDeci(String str,
                      int base) {
        int len = str.length();
        int power = 1; // Initialize
        // power of base
        int num = 0; // Initialize result
        int i;

        // Decimal equivalent is
        // str[len-1]*1 + str[len-2] *
        // base + str[len-3]*(base^2) + ...
        for (i = len - 1; i >= 0; i--) {
            // A digit in input number
            // must be less than
            // number's base
            if (val(str.charAt(i)) >= base) {
                System.out.println("Invalid Number");
                return -1;
            }

            num += val(str.charAt(i)) * power;
            power = power * base;
        }

        return num;
    }
}
