# most_common_words.py

import sys
from collections import Counter

# pass in number of words as first argument
try:
    num_words = int(sys.argv[1])
except:
    print("usage: most_common_words.py num_words")
    sys.exit(1) 		# non-zero exit code indicates error

counter = Counter(word.lower()				# lowercase words
                  for line in sys.stdin			#
                  for word in line.strip().split() 	# split on spaces
                  if word) 				# skip empty 'words'

print(counter.most_common(num_words))

for word, count in counter.most_common(num_words):
    sys.stdout.write(str(count))
    sys.stdout.write("\t")
    sys.stdout.write(word)
    sys.stdout.write("\n")