import sequtils,algorithm,sugar
proc getchar_unlocked():char {. importc:"getchar_unlocked",header: "<stdio.h>" .}
proc scan(): int =
  while true:
    let k = getchar_unlocked()
    if k < '0' or k > '9': break
    result = 10 * result + k.ord - '0'.ord

template useBinaryHeap() =
  type
    BinaryHeap*[T] = object
      nodes: seq[T]
      compare: proc(x,y:T):int
      popchunk: bool
  proc newBinaryHeap*[T](compare:proc(x,y:T):int): BinaryHeap[T] =
    BinaryHeap[T](nodes:newSeq[T](),compare:compare,popchunk:false)
  proc compareNode[T](h:BinaryHeap[T],i,j:int):int = h.compare(h.nodes[i],h.nodes[j])
  proc size*[T](h:BinaryHeap[T]):int = h.nodes.len() - h.popchunk.int
  proc items*[T](h:var BinaryHeap[T]):seq[T] =
    if h.popchunk : discard h.popimpl()
    return h.nodes
  proc top*[T](h:var BinaryHeap[T]): T =
    if h.popchunk : discard h.popimpl()
    return h.nodes[0]
  proc push*[T](h:var BinaryHeap[T],node:T):void =
    if h.popchunk :
      h.nodes[0] = node
      h.shiftdown()
    else: h.pushimpl(node)
  proc pop*[T](h:var BinaryHeap[T]):T =
    if h.popchunk: discard h.popimpl()
    h.popchunk = true
    return h.nodes[0]

  proc shiftdown[T](h:var BinaryHeap[T]): void =
    h.popchunk = false
    let size = h.nodes.len()
    var i = 0
    while true :
      let L = i * 2 + 1
      let R = i * 2 + 2
      if L >= size : break
      let child = if R < size and h.compareNode(R,L) <= 0 : R else: L
      if h.compareNode(i,child) <= 0: break
      swap(h.nodes[i],h.nodes[child])
      i = child

  proc pushimpl[T](h:var BinaryHeap[T],node:T):void =
    h.nodes.add(node) #末尾に追加
    var i = h.nodes.len() - 1
    while i > 0: # 末尾から木を整形
      let parent = (i - 1) div 2
      if h.compare(h.nodes[parent],node) <= 0: break
      h.nodes[i] = h.nodes[parent]
      i = parent
    h.nodes[i] = node

  proc popimpl[T](h:var BinaryHeap[T]):T =
    result = h.nodes[0] # rootと末尾を入れ替えて木を整形
    h.nodes[0] = h.nodes[^1]
    h.nodes.setLen(h.nodes.len() - 1)
    h.shiftdown()

useBinaryHeap()

proc parseLine(): tuple[x,y:int] =
  result.x = scan() * 1440 + scan() * 60 + scan()
  result.y = scan() * 1440 + scan() * 60 + scan()

let n = scan()
let m = scan()
let U = newSeqWith(m,parseLine()).sortedByIt(it.y)
# var pq = newBinaryHeap[tuple[a,b:int]]((x,y)=> (
#   if x.b != y.b: y.b - x.b else:

# ))
# for i in 0..<n:pq.push(0)
var preY = newSeq[int](n)
var ans = 0
for u in U:
  for i in 0..<n: # preYの遅い順に見るべき
    if preY[i] >= u.x: continue
    preY[i] = u.y
    ans += 1
    preY.sort(cmp,Descending)
    break
echo ans