#include<bits/stdc++.h>

 using namespace std;

 const int N = 2e5+;

 typedef long long ll;

 char s[N];

 int main()

 {

     scanf("%s",s);

     ll cnt =  ;

     ll ans =  , i =  ;

     int len = strlen(s);

     while ( s[i] ) {

         if( s[i] == 'A' ){

             //printf("#1 %d \n" ,i);

             cnt ++ ;

             i++ ;

         }else if ( s[i] == 'B' && s[i+] == 'C' ){

             //printf("#2 %d \n" ,i);

             ans = ans + cnt ;

             i+= ;

             if( i >= len ) break ;

         }else if ( s[i] == 'B' || s[i] == 'C' || s[i] == '\0' ){

             cnt =  ;

             i++ ;

         }

     }

     //ans = ans + cnt ;

     printf("%lld\n",ans);

 }