N=int(input())
A=sorted(map(int,input().split()))
DP=dict()
ANS=0
SET=set(A)

a=0
i=0
for a in A:
    if a in DP:
        DP[a]+=1
    else:
        DP[a]=1
    if a-1 in DP:
        DP[a+1]=DP[a-1]

ANS=0
for x in DP:
    ANS+=DP[x]
print(ANS)