bufio_scanner = []


def main():
    n = int(fmt_scan())
    a = [int(fmt_scan()) for _ in range(n)]

    a.sort()
    ans = n
    k = 0
    for i in range(n):
        if i == 0:
            continue
        for k in range(2):
            try:
                if a[i - 1 - k] + 1 < a[i]:
                    ans -= 1
            except:
                pass
    print(ans)


def fmt_scan() -> str:
    sc = bufio_scanner
    if len(sc) == 0:
        for v in input().split()[::-1]:
            sc.append(v)
    res = sc[-1]
    sc.pop()
    return res


main()