#include "bits/stdc++.h"
using namespace std;
#define ll long long
#define endl '\n'
#define rep(i, n) for(int i = 0; i < (int)(n); i++)
#define rep2(i,a,b) for(int i=int(a);i<int(b);i++)
#define pb emplace_back
#define all(x) (x).begin(),(x).end()
ll mod=1e9+7;
ll mod2=998244353;
const int INF=1e9;

signed main(){
	string s;
	cin>>s;
	if(s.size()<3){
		cout<<0<<endl;
		return 0;
	}
	ll ans=0;
	ll cnt=0;
	rep(i,s.size()-1){
		if(s[i]=='A')cnt++;
		else if(s[i]=='B'&&s[i+1]=='C'){
			ans+=cnt;
			i++;
		}else cnt=0;
	}
	cout<<ans<<endl;
}


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