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: Time Limit Exceeded)

#include <stdio.h>
#include <string.h>

int main(){
    char S[200000];
    scanf("%s", S);
    int N = strlen(S), ans=0, b_ans , i, j;

    int start=0, cnt=0, end=N-2, endf;
    for(i=0; 1; i++){
        b_ans = ans;
        cnt = 0;
        for(j=start; j<end; j++){
            if (S[j]=='A' && S[j+1] == 'B' && S[j+2] == 'C'){
                S[j]='B';
                S[j+1] = 'C';
                S[j+2] = 'A';
                ans++;
                if (cnt=0) start = j-2;
                if (start<0) start = 0;
                endf = j;
                cnt++;
            }
        }
        end = endf+2;
        if (end >= N-2) end = N-2;
        if (b_ans == ans) break;
    }

    printf("%d",  ans);

    return 0;
}