n = int(input())
a = []
for i in range(n):
    aa = int(input())
    a.append(aa)
a.sort()
f = False
res = 0
for i in range(n-1):
    if f:
        if a[i+1]-a[i] > 1:
            pass
        else:
            tmp = 0
            f = False
            res += 1
    else:
        if a[i+1]-a[i] > 1:
            f = True
        else:
            res += 1
res += 1
print(res)