S = input()
S = S[::-1].replace("11", "X")[::-1].split("1")

answer = 0
prev = 0
for c in S:
    cnt = 0
    for x in c:
        if x == "X":
            cnt += 1
        elif x == "0":
            answer += cnt + prev
    prev += cnt

print(answer)

# 011101110