926C - Is This a Zebra - CodeForces Solution

n = int(input())
la = -1
cnt = 0
flg = True
lac = -1
s = input().split()
for i in range(n):
  x = int(s[i])
  if (x == lac):
    cnt += 1
  else:
    if (la != -1 and la != cnt):
      flg = False
      break
    else:
      if (cnt != 0):
        la = cnt
      cnt = 1
      lac = x
if (flg == False or (la != -1 and la != cnt)):
  print('NO')
else:
  print('YES')