file = open('18.txt')
text = file.readline()
Max = 0
d = dict()
for i in range(2, len(text) - 2):
    if text[i - 2] + text[i - 1] == 'CB' and text[i + 1] + text[i + 2] == 'BC':
        if text[i] in d:
            d[text[i]] += 1
            Max = max(Max, d[text[i]])
        else:
            d[text[i]] = 1
for elem in d:
    if d[elem] == Max:
        print(elem)
print(Max)