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


		//~~~~~~~~~~~~~~~~~~~~~~~@@@@@@@@@@@@@@@_____________K_____S_____J__________@@@@@@@@@@@@@@@@@@@@@@@@@@@@~~~~~~~~~~~~~~~~~~~~~~~~~~
		//Date:00/00/17
		//-------------


import java.util.*;
import java.io.*;

/*

    [[[[[[[[[[[[[[[      ]]]]]]]]]]]]]]]
    [::::::::::::::      ::::::::::::::]
    [::::::::::::::      ::::::::::::::]
    [::::::[[[[[[[:      :]]]]]]]::::::]
    [:::::[                      ]:::::]
    [:::::[                      ]:::::]
    [:::::[                      ]:::::]
    [:::::[                      ]:::::]
    [:::::[    CODE YOUR LIFE    ]:::::]
    [:::::[   Kripa Shankar jha  ]:::::]
    [:::::[                      ]:::::]
    [:::::[                      ]:::::]
    [:::::[                      ]:::::]
    [:::::[                      ]:::::]
    [::::::[[[[[[[:      :]]]]]]]::::::]
    [::::::::::::::      ::::::::::::::]
    [::::::::::::::      ::::::::::::::]
    [[[[[[[[[[[[[[[      ]]]]]]]]]]]]]]]
*/

public class prob3{
			
	  static int mod=(int)1E9+7;	
	  static boolean visi[]=new boolean[1000006];;
	  static int min=Integer.MAX_VALUE;	
	  static int max=Integer.MIN_VALUE;	

	  static int arr[]=new int[1000005];;
	  static ArrayList<Integer> list[]=new ArrayList[1000005];

	  static Parser sc=new Parser(System.in);
	  static PrintWriter out = new PrintWriter(new BufferedOutputStream(System.out));
	
	public static void main(String[] args) throws IOException {

		int n=sc.nextInt();

		int f=1,s=2,t=3,temp;

		boolean fl=false;
		
		for(int i=1;i<=n;i++){
			int in=sc.nextInt();
			if(in==t){
				fl=true;
			}
			else if(in==f){
				temp=t;
				t=s;
				s=temp;
			}
			else if(in==s){
				
				temp=t;
				t=f;
				f=temp;

			}
		}

		if(fl==true){
			System.out.println("NO");
		}
		else{
			System.out.println("YES");
		}

	}

	

	public static void dfs(int t){

		Stack<Integer> st=new Stack<>();
		
		visi[t]=true;
		st.add(t);
		
		while(!st.isEmpty()){

			  int v=st.pop();	
				
			  min=Math.min(min,arr[v]);
				
			  for(int i=0;i<list[v].size();i++){

			  	if( visi[list[v].get(i)] ==false){
			  		
			  		st.add(list[v].get(i));
			  		visi[list[v].get(i)]=true;
			  	
			  	 }
			  }
		}


	}



	//___________________________Fast-Input_Output-------------------******************* 
	

	static class Parser {
        final private int BUFFER_SIZE = 1 << 20;  // 2^16, a good compromise for some problems
        private InputStream din;    // Underlying input stream
        private byte[] buffer;      // Self-maintained buffer
        private int bufferPointer;  // Current read position in the buffer
        private int bytesRead;      // Effective bytes in the buffer read from the input stream
        private SpaceCharFilter filter;
        public Parser(InputStream in) {
            din = in;
            buffer = new byte[BUFFER_SIZE];
            bufferPointer = bytesRead = 0;
        }

        /**
         * Read the next integer from the input stream.
         * @return The next integer.
         * @throws IOException
         */
        public int nextInt() throws IOException {
            int result = 0;
            byte c = read();
            while (c <= ' ') c = read();
            boolean neg = (c == '-');
            if (neg) c = read();
				while (c >= '0' && c <= '9') {
                result = result * 10 + c - '0';
                c = read();
            }
			if (neg) return -result;
            	return result;
        }

        public int nextLong() throws IOException {
            int result = 0;
            byte c = read();
            while (c <= ' ') c = read();
            boolean neg = (c == '-');
            if (neg) c = read();
				while (c >= '0' && c <= '9') {
                result = result * 10 + c - '0';
                c = read();
            }
			if (neg) return -result;
            	return result;
        }

        public String nextLine()throws IOException {
				int c = read();
				while (isSpaceChar(c))
					c = read();
				StringBuilder res = new StringBuilder();
				do {
					res.appendCodePoint(c);
					c = read();
				} while (!isEndOfLine(c)==true);
				return res.toString();
			}

			public boolean isSpaceChar(int c) {
				if (filter != null)
					return filter.isSpaceChar(c);
				return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
			}
	 
			private boolean isEndOfLine(int c) {
				return c == '\n' || c == '\r' || c == -1;
			}
			public interface SpaceCharFilter {
				public boolean isSpaceChar(int ch);
			}


        /**
         * Read the next byte of data from the input stream.
         * @return the next byte of data, or -1 if the end of the stream is reached.
         * @throws IOException if an I/O error occurs.
         */
        public byte read() throws IOException {
            if (bufferPointer == bytesRead)
                fillBuffer();
            return buffer[bufferPointer++];
        }

        /**
         * Read data from the input stream into the buffer
         * @throws IOException if an I/O error occurs.
         */
        private void fillBuffer() throws IOException {
            bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE);
            if (bytesRead == -1)
                buffer[0] = -1;
        }
    }
}