n = int(input())
a = [int(input()) for _ in range(n)]
a.sort()
if n == 0:
    print(0)
else:
    count = 1
    current = a[0]
    for num in a[1:]:
        if current + 1 < num:
            current = num
        else:
            count += 1
            current = num
    print(count)