task 4

def num_taxis(reqs):
    data = []
    taxis = len(reqs)
    for i in reqs:
        data.extend(i)
    print(data)
    print(taxis)
    for i in data:

      if (data.index(i) % 2 != 0):
          print("INDEX = ", data.index(i))
          for k in data:
              if (data.index(k) % 2 == 0):
                  if i < k:
                      print("I = ", i)
                      print("K = ", k)
                      taxis = taxis - 1
                      print("taxis =", taxis)
    return taxis