#include<bits/stdc++.h>
#define ll long long
using namespace std;
const ll N=2e6+5,mod=998244353;
string s;
ll cnt,ans;
signed main(){
	ios::sync_with_stdio(0),cout.tie(0),cin.tie(0);
	cin>>s;
	for(int i=0;i<s.size();i++){
		if(i+1<s.size() && s[i]=='B' && s[i+1]=='C'){
			ans+=cnt;
			i++;
		}else if(s[i]=='A') cnt++;
		else cnt=0;
	}
	cout<<ans;
	return 0;
}