from collections import Counter
import sys


uniq_chars = Counter()
if len(sys.argv) >= 2:
    text = open(sys.argv[1], 'r+')
else:
    while True:
        f = input('Введите пожалуйста имя файла: ')
        try:
            text = open(f, 'r+')
            break
        except FileNotFoundError:
            print('Вы не ввели имя файла, или такого файла не существует')
            continue


for x in text:
    uniq_chars += Counter(x.strip().lower())

text.close()
uniq_words = uniq_chars.most_common(2)

if uniq_words [0][0] == ' ':
    print("In this file, the most common letter is ", uniq_words[1][0],
          "it repeated ", uniq_words[1][1], "times")
else:
    print('In this file, the most common letter is ', uniq_words[0][0],
          'it repeated ', uniq_words[0][1], 'times')