bufio_scanner = []


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

    ans = n
    d = [0, 0]
    for v in a:
        d.sort()
        if v <= max(d) - 2:
            ans -= 1
        d[0] = v
    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()