N = list(input())
inf = 10 ** 18
dp0 = [inf] * (len(N) + 1)
dp1 = [inf] * (len(N) + 1)
dp0[0], dp1[0] = 0, 1
for i, n in enumerate(N, 1):
    if n == "0":
        dp0[i] = min(dp0[i], dp0[i - 1])
        dp1[i] = min(dp1[i], dp1[i - 1] + 1, dp0[i - 1] + 1)
    else:
        dp0[i] = min(dp0[i], dp0[i - 1] + 1, dp1[i - 1] + 1)
        dp1[i] = min(dp1[i], dp1[i - 1])

print(dp0[-1])