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


/*


        HARSH KHATRI
        DA-IICT

                      */

import java.io.*;
import java.util.*;
import java.lang.*;
import java.util.Scanner;
import java.util.Arrays;
import java.util.List;
import java.util.ArrayList;

public class CF893A {

    static FasterScanner in = new FasterScanner();
    static PrintWriter out = new PrintWriter(System.out);
    static boolean debug = false;

    public static void main(String[] args) {

        int n = in.nextInt(), a[] = new int[n], spec, win, tmp;
        int i, j, k;
        boolean valid = true;
        spec = 3; win  = tmp = 0;

        for(i=0; i<n; i++) {
            win = in.nextInt();
            if(debug) out.println(spec+" "+win);
            if(win==spec) { valid = false; break; }
            else {
                for(j=1; j<=3; j++) {
                    if(j!=win && j!=spec) tmp=j;
                }
                spec = tmp;
            }
        }

        out.println( valid ? "YES" : "NO" );
        out.close();
    }
}

class Pair implements Comparator<Pair> {

    int x;
    int y;
    int z;

    Pair() {}

    Pair(int a, int b) {
        x = a;
        y = b;
    }

    Pair(int a, int b, int c) {
        x = a;
        y = b;
        z = c;
    }

    @Override
    public int compare(Pair p, Pair q) {
        return (p.x-q.x);
    }

    @Override
    public boolean equals(Object object) {

        if(object!=null && object instanceof Pair) {
            return (this.x==((Pair)object).x && this.y==((Pair)object).y && this.z==((Pair)object).z);
        }

        return false;
    }

    @Override
    public int hashCode() {
        return Objects.hash(x, y, z);
    }
}

class FasterScanner {
    private byte[] buf = new byte[1024];
    private int curChar;
    private int snumChars;

    public int read() {
      if (snumChars == -1)
    throw new InputMismatchException();
      if (curChar >= snumChars) {
    curChar = 0;
    try {
      snumChars = System.in.read(buf);
    } catch (IOException e) {
      throw new InputMismatchException();
    }
    if (snumChars <= 0)
      return -1;
      }
      return buf[curChar++];
    }

    public double nextDouble() {
      return Double.parseDouble(this.nextString());
    }

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

    public char nextChar() {
        int c = read();
        while (isSpaceChar(c))
            c = read();
        return (char)c;
    }

    public String nextString() {
      int c = read();
      while (isSpaceChar(c))
    c = read();
      StringBuilder res = new StringBuilder();
      do {
    res.appendCodePoint(c);
    c = read();
      } while (!isSpaceChar(c));
      return res.toString();
    }

    public long nextLong() {
      int c = read();
      while (isSpaceChar(c))
    c = read();
      int sgn = 1;
      if (c == '-') {
    sgn = -1;
    c = read();
      }
      long res = 0;
      do {
    if (c < '0' || c > '9')
      throw new InputMismatchException();
    res *= 10;
    res += c - '0';
    c = read();
      } while (!isSpaceChar(c));
      return res * sgn;
    }

    public int nextInt() {
      int c = read();
      while (isSpaceChar(c))
    c = read();
      int sgn = 1;
      if (c == '-') {
    sgn = -1;
    c = read();
      }
      int res = 0;
      do {
    if (c < '0' || c > '9')
      throw new InputMismatchException();
    res *= 10;
    res += c - '0';
    c = read();
      } while (!isSpaceChar(c));
      return res * sgn;
    }

    public int[] nextIntArray(int n) {
      int[] arr = new int[n];
      for (int i = 0; i < n; i++) {
    arr[i] = nextInt();
      }
      return arr;
    }

    public long[] nextLongArray(int n) {
      long[] arr = new long[n];
      for (int i = 0; i < n; i++) {
    arr[i] = nextLong();
      }
      return arr;
    }

    private boolean isSpaceChar(int c) {
      return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
    }

    private boolean isEndOfLine(int c) {
      return c == '\n' || c == '\r' || c == -1;
    }
}