def solve(arr):
  events = dict()
  for a in arr:
    if a[0] not in events:
      events[a[0]] = 0
    events[a[0]] += 1
    if a[1] not in events:
      events[a[1]] = 0
    events[a[1]] -= 1
  n = 0
  max = 0
  for e, v in sorted(events.items()):
    n += v
    if n > max:
      max = n
  return max

print(solve([(30, 75), (0, 50), (60, 150)]))