mod = 1000000007
eps = 10**-9


def main():
    import sys
    input = sys.stdin.readline

    S = input().rstrip('\n')
    A = [int(s) for s in S[::-1]] + [0]
    N = len(A)

    ans = 0
    for i in range(N-1):
        if A[i]:
            if not A[i+1]:
                ans += 1
            else:
                ans += 1
                j = i
                while True:
                    if A[j] == 1:
                        A[j] = 0
                        j += 1
                    else:
                        A[j] = 1
                        break
    if A[-1]:
        ans += 1
    print(ans)


if __name__ == '__main__':
    main()