N = int(input())
A = []
for i in range(N):
    A.append(int(input()))
ans = N
A.sort()
smp = 0
for i in range(N):
    if i == 0:
        smp = A[i]
    else:
        if smp + 1 < A[i]:
            ans -= 1
            smp = A[i]
        else:
            smp = A[i]
print(ans)