import sys
sys.setrecursionlimit(10**6)
N = list(input())
ans = 0
cnt = 0
N.reverse()
n = len(N)
memo = [[-1, -1] for i in range(n)]
def dfs(i, b):
    if i == n:
        return b
    if memo[i][b] != -1:
        return memo[i][b]
    r = 10**6
    if N[i] == '1':
        if b:
            r = min(r, dfs(i+1, 1))
        else:
            r = min(r, min(dfs(i+1, 0), dfs(i+1, 1)) + 1)
    else:
        if b:
            r = min(r, min(dfs(i+1, 0), dfs(i+1, 1)) + 1)
        else:
            r = min(r, dfs(i+1, 0))
    memo[i][b] = r
    return r
print(dfs(0, 0))