S = input().strip()
A = []
flag = 0
for i in range(len(S)):
    if S[i]=="0":
        A.append(0)
        flag = 0
    elif flag==0 and S[i]=="1":
        flag = 1
    elif flag==1 and S[i]=="1":
        A.append(1)
        flag = 0
cnt = 0
ans = 0
for i in range(len(A)):
    if A[i]==1:
        cnt += 1
    else:
        ans += cnt
print(ans)