from collections import Counter
def count(s):
    dic = Counter()
    diff = (0,0)
    dic[diff] += 1
    result = 0
    for c in s:
        if c == 'A':
            diff = (diff[0]-1,diff[1]-1)
        elif c == 'B':
            diff = (diff[0]+1,diff[1])
        else:
            diff = (diff[0],diff[1]+1)
        result += dic[diff]
        dic[diff] += 1
    return result


print(count('CBACBACBA'))