#include <bits/stdc++.h>
using namespace std;

int main()
{
int i;
int iPos;
int iSum;
char S[ 20 ];
char C;

	cin >> S;

	iPos = 0;
	iSum = 0;
	i = 0;
	while( ( C = S[ i ] ) != '\0' )
	{
		if( C == 'A' )
		{
			iSum += i - iPos;
			iPos++;
		}
		
		i++;
	}

	cout << iSum << endl;

	return 0;
}