#include #define rep(i,n)for(long long i=0;i<(long long)(n);++i) #define all(a) a.begin(), a.end() using namespace std; typedef long long ll; typedef unsigned long long ull; typedef pair P; template inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; } template inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; } const ll MOD=1000000007; const ll INF=1e18; const int MAX=510000; const double pi=acos(-1); int dx[8] = {1,0,-1,0,1,1,-1,-1}; int dy[8] = {0,1,0,-1,-1,1,1,-1}; int main(){ cin.tie(0); ios::sync_with_stdio(false); string s; cin >> s; int n = s.size(); int ans = 0, sum = 0; rep(i,n){ if(s[i] == 'A'){ ans += i-sum; ++sum; } } cout << ans << endl; return 0; }