from operator import itemgetter
from itertools import *
from bisect import *
from collections import *
from heapq import *
import sys

sys.setrecursionlimit(10**6)
int1 = lambda x: int(x)-1
p2D = lambda x: print(*x, sep="\n")
def II(): return int(sys.stdin.buffer.readline())
def MI(): return map(int, sys.stdin.buffer.readline().split())
def LI(): return list(map(int, sys.stdin.buffer.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def MI1(): return map(int1, sys.stdin.buffer.readline().split())
def LI1(): return list(map(int1, sys.stdin.buffer.readline().split()))
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def BI(): return sys.stdin.buffer.readline().rstrip()
def SI(): return sys.stdin.buffer.readline().rstrip().decode()
def inval(ni, nj, h, w):
    if ni < 0 or ni >= h or nj < 0 or nj >= w: return True
    return False
dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
inf = 10**16

n = II()
aa = LI()

dp=defaultdict(int)
aa.sort()
for a in aa:
    dp[a]+=1
    if a-1 in dp:dp[a+1]=dp[a-1]

ans=sum(dp.values())
print(ans)