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 Perl (v5.18.2) (judge verdict: Accepted)

use strict;
use warnings;

chomp(my $s = <>);

my $cnt = 0;

$s =~ s/BC/D/g;

my @list = split /[BC]/, $s;
foreach my $item (@list) {
	
	next if $item eq "";
	#print $item, "\n";
	
	my $str = $item;
	while ($str =~ m/AD/) {
		$str =~ s/(.*?)A/A/;
		$str =~ s/(A+)(D+)/$1/;
		my $add = (length $1) * (length $2);
		$cnt += $add;
	}
}

print $cnt, "\n";