S = list( input() )
N = len(S)

p = 0
q = 0

res = 0

for i in range(N) :
    if S[i] == "1" :
        if q == 0 :
            q += 1
        else :
            q = 0
            p += 1
    else :
        res += p
        q = 0

print( res )