import sequtils,algorithm
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

proc parseLine(): tuple[x,y:int] =
  let (x1,x2,x3) = (scan(),scan(),scan())
  let (y1,y2,y3) = (scan(),scan(),scan())
  result.x = x3 + x2 * 60 + x1 * 1440
  result.y = y3 + y2 * 60 + y1 * 1440

let n = scan()
let m = scan()
let U = newSeqWith(m,parseLine()).sortedByIt(it.y)
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