def main():
  from sys import stdin
  readline=stdin.readline
  n = int(readline())
  A = [int(readline()) for _ in range(n)]
  A.sort()
  cnt = 0
  for i in range(n-1):
    if A[i+1] - A[i] <= 2:
      cnt += 1
  print(cnt + 1)
main()