n = str(input())
INF = 10**18
n = list(n)
n.reverse()
n += ['0']
dp = [INF]*2
dp[0] = 0
for c in n:
    nx = [INF]*2
    if c == '0':
        nx[0] = min(nx[0], dp[0])
        nx[0] = min(nx[0], dp[1]+1)
        nx[1] = min(nx[1], dp[1]+1)
    else:
        nx[0] = min(nx[0], dp[0]+1)
        nx[1] = min(nx[0], dp[0]+1)
        nx[1] = min(nx[1], dp[1])
    dp = nx
print(min(dp))