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: Wrong Answer)

#include<stdio.h>
int main(void) {
  int cnt = 0;
  int n;
  char s[200001];
  scanf("%s", s);
  for(int i = 0; s[i+2] != '\0'; i++) {
    if(s[i] == 'A' && s[i+1] == 'B' && s[i+2] == 'C') {
      //ABC見つけた時の処理
      cnt++;
      s[i] = 'B';
      s[i+1] = 'C';
      s[i+2] = 'A';
      if(i != 0 && s[i-1] == 'A') {
        n = i-1;
        s[n+2] = 'A';
        while(n >= 0) {
          if(s[n] == 'A') {
            cnt++;
            s[n] = 'B';
            s[n+1] = 'C';
            // s[n+2] = 'A';
            n--;
          }else{
            break;
          }
        }
      }//前にA
    }
  }
  printf("%d", cnt);
  return 0;
}