with open("source.txt") as f:
    data = f.read()
    words = data.split()
    word_dict = dict()
    for word in words:
        if word in word_dict:
            word_dict[word] += 1
        else:
            word_dict[word] = 1
    max = 0
    for key, value in word_dict.items():
        if value > max:
            max = value
    moda = []
    for key, value in word_dict.items():
        if value == max:
            moda.append(key)
    print(max)
    for el in moda:
        print(el)