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
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1
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1
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1
1
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2
2
1
1
1
3
1
3
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1
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3
3
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1
1
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3
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1
2
1
1
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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
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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

"""
Author    : co_devil Chirag Garg
Institute : JIIT
"""

from __future__ import division, print_function
import itertools, os, sys, threading
from collections import deque, Counter, OrderedDict, defaultdict
import heapq
from math import ceil,floor,log,sqrt,factorial,pow,pi
# from bisect import bisect_left,bisect_right
# from decimal import *,threading
"""from io import BytesIO, IOBase
if sys.version_info[0] < 3:
    from __builtin__ import xrange as range
    from future_builtins import ascii, filter, hex, map, oct, zip
else:
    from builtins import str as __str__
    str = lambda x=b'': x if type(x) is bytes else __str__(x).encode()
BUFSIZE = 8192
class FastIO(IOBase):
    newlines = 0
    def __init__(self, file):
        self._buffer = BytesIO()
        self._fd = file.fileno()
        self._writable = 'x' in file.mode or 'r' not in file.mode
        self.write = self._buffer.write if self._writable else None

    def read(self):
        return self._buffer.read() if self._buffer.tell() else os.read(self._fd, os.fstat(self._fd).st_size)

    def readline(self):
        while self.newlines == 0:
            b, ptr = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE)), self._buffer.tell()
            self._buffer.seek(0, 2), self._buffer.write(b), self._buffer.seek(ptr)
            self.newlines += b.count(b'\n') + (not b)
        self.newlines -= 1
        return self._buffer.readline()

    def flush(self):
        if self._writable:
            os.write(self._fd, self._buffer.getvalue())
            self._buffer.truncate(0), self._buffer.seek(0)
sys.stdin, sys.stdout = FastIO(sys.stdin), FastIO(sys.stdout)
input = lambda: sys.stdin.readline().rstrip(b'\r\n')

def print(*args, **kwargs):
    sep, file = kwargs.pop('sep', b' '), kwargs.pop('file', sys.stdout)
    at_start = True
    for x in args:
        if not at_start:
            file.write(sep)
        file.write(str(x))
        at_start = False
    file.write(kwargs.pop('end', b'\n'))
    if kwargs.pop('flush', False):
        file.flush()

"""


def ii(): return int(input())
def si(): return str(input())
def mi(): return map(int,input().split())
def li(): return list(mi())


abc = 'abcdefghijklmnopqrstuvwxyz'
abd = {'a': 0, 'b': 1, 'c': 2, 'd': 3, 'e': 4, 'f': 5, 'g': 6, 'h': 7, 'i': 8, 'j': 9, 'k': 10, 'l': 11, 'm': 12,
       'n': 13, 'o': 14, 'p': 15, 'q': 16, 'r': 17, 's': 18, 't': 19, 'u': 20, 'v': 21, 'w': 22, 'x': 23, 'y': 24,
       'z': 25}
mod = 1000000007
dx, dy = [-1, 1, 0, 0], [0, 0, 1, -1]
def getKey(item): return item[0]
def sort2(l): return sorted(l, key=getKey)
def d2(n, m, num): return [[num for x in range(m)] for y in range(n)]
def isPowerOfTwo(x): return (x and (not (x & (x - 1))))
def decimalToBinary(n): return bin(n).replace("0b", "")
def ntl(n): return [int(i) for i in str(n)]
def powerMod(x, y, p):
    res = 1
    x %= p
    while y > 0:
        if y & 1:
            res = (res * x) % p
        y = y >> 1
        x = (x * x) % p
    return res
def gcd(x, y):
    while y:
        x, y = y, x % y
    return x
# For getting input from input.txt file
# sys.stdin = open('input.txt', 'r')

# Printing the Output to output.txt file
# sys.stdout = open('output.txt', 'w')

graph = defaultdict(list)
visited = [0] * 1000000
col = [-1] * 1000000
def dfs(v, c):
    if visited[v]:
        if col[v] != c:
            print('-1')
            exit()
        return
    col[v] = c
    visited[v] = 1
    for i in graph[v]:
        dfs(i, c ^ 1)

def bfs(d,v):
    q=[]
    q.append(v)
    visited[v]=1
    while len(q)!=0:
        x=q[0]
        q.pop(0)
        for i in d[x]:
            if visited[i]!=1:
                visited[i]=1
                q.append(i)
        print(x)
def make_graph():
    d={}
    v,e=mi()
    for i in range(e):
        x,y=mi()
        if x not in d.keys():
            d[x]=[y]
        else:
            d[x].append(y)
        if y not in d.keys():
            d[y] = [x]
        else:
            d[y].append(x)
    return d
def gr2(n):
    d={}
    for i in range(n):
        x,y=mi()
        if x not in d.keys():
            d[x]=[y]
        else:
            d[x].append(y)
    return d

n=ii()
l=[]
for i in range(n):
    x=ii()
    l.append(x)
s=[3]
a=1
b=2
f=0
for i in range(n):
    if s[i]==l[i]:
        f=1
        print("NO")
        break
    else:
        a=l[i]
        b=s[i]
        if l[i]==1 and s[i]==3:
            s.append(2)
        elif l[i]==1 and s[i]==2:
            s.append(3)
        elif l[i]==2 and s[i]==3:
            s.append(1)
        elif l[i]==2 and s[i]==1:
            s.append(3)
        elif l[i]==3 and s[i]==1:
            s.append(2)
        elif l[i]==3 and s[i]==2:
            s.append(1)
if f==0:
    print("YES")