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 C (GCC 5.4.1) (judge verdict: Accepted)

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#include <math.h>

int main(void){
    char s[200500];
    scanf("%s",s);
    long long ans=0,counta=0;
    for (int i=0; i<strlen(s); i++){
        if (s[i]=='A'){
            counta++;
        } else if (s[i]=='B'){
            if (s[i+1]=='C'){
                ans+=counta;
                i++;
            } else {
                counta=0;
            }
        } else {
            counta=0;
        }
    }
    printf("%lld\n",ans);
    return 0;
}