def main():
  from sys import stdin
  readline=stdin.readline
  n = int(readline())
  A = [int(readline()) for _ in range(n)]
  A.sort()
  ans = 1
  flag = True
  for i in range(n-1):
    if A[i]+1 < A[i+1]:
      if flag:
        continue
      flag = True
      ans += 1
    else:
      flag = False
      ans += 1
  print(ans)
main()