#your code goes here
#new
N=int(input())
A=[int(i)for i in input().split()]
A.sort()
C=0
if A[0]!=A[1]:
    C+=1
for i in range(1,N-2):
    if A[i]!=[i-1] and A[i]!=[i+1]:
        C+=1
if A[i-2]!=A[i-1]:
    C+=1
print(C)