class Bit:
    def __init__(self, n):
        self.size = n
        self.tree = [0] * (n + 1)
 
    def _add(self, i, x):
        while i <= self.size:
            self.tree[i] += x
            i += i & -i
            
    def _sum(self, i):
        s = 0
        while i > 0:
            s += self.tree[i]
            i -= i & -i
        return s

t = input()
t=t.translate(str.maketrans({'B': 'A', 'A': 'B'}))
b=Bit(200)
ans = 0
for i in range(len(t)):
    ans += b._sum(ord(t[i])-1)
    b._add(ord(t[i]),1)

print(ans)