import re

P = re.compile('B')

def f(s):
    t = len(s) - 1
    if t == 0:
        return 0
    l = [t - m.start() for m in P.finditer(s)]
    t = len(l) - 1
    return sum(i-j for i,j in zip(l, range(t,-1,-1)))

s = input()
print(f(s))