n = list(map(int,input()))[::-1] + [0]
inf = 10**10
dp = [0,inf]

for b in n:
    ndp = [inf,inf]
    if b == 0:
        ndp[0] = min(dp[0],dp[1]+1)
        ndp[1] = dp[1]+1
    else:
        ndp[0] = dp[0]+1
        ndp[1] = min(dp[0]+1,dp[1])
    dp = ndp
print(min(dp[0],dp[1]+1))