max_num, n = map(int,input().split()) li = [] se = set() left = right = step = 0 li2 = list(map(int,input().split())) for i in li2: if i in se: continue if right-left >= max_num: se.remove(li[left]) left += 1 se.add(i) li.append(i) right+=1 step +=1 print(step)