Problem:
Score : 600 points

Problem Statement

You are given a string s consisting of A, B and C.

Snuke wants to perform the following operation on s as many times as possible:

Choose a contiguous substring of s that reads ABC and replace it with BCA.

Find the maximum possible number of operations.

Constraints

1 \leq |s| \leq 200000

Each character of s is A, B and C.

Input

Input is given from Standard Input in the following format:

s

Output

Find the maximum possible number of operations.

Sample Input 1

ABCABC

Sample Output 1

3

You can perform the operations three times as follows: ABCABC → BCAABC → BCABCA → BCBCAA. This is the maximum result.

Sample Input 2

C

Sample Output 2

0

Sample Input 3

ABCACCBABCBCAABCB

Sample Output 3

6

Solution in Python (3.8.2) (judge verdict: Accepted)

s=input()
t=''
i=0
while(i<len(s)):
    if i<len(s)-1 and s[i:i+2]=='BC':
        t+='D'
        i+=2
    else:
        t+=s[i]
        i+=1
t=t[::-1]
N=len(t)
i=0
ans=0
while(i<N):
    if t[i]=='D':
        j=i
        cnt=0
        while(j<N and t[j]!='B' and t[j]!='C'):
            if t[j]=='D':
                cnt+=1
            else:
                ans+=cnt
            j+=1
        i=j
    i+=1
print(ans)