m = int(input())
n = int(input())
a = [int(input()) for i in range(n)]
cnt = 0
while a != []:
    _max = max(a)
    _min = min(a)
    if _max + _min <= m:
        a.remove(_max)
        a.remove(_min)
    else:
        a.remove(_max)
    cnt += 1
print(cnt)