def solution(n):
    # 1.  *0: /= 2
    # 2. *01: -= 1
    # 3. *11: += 1

    # state 0: *0
    # state 1: *1
    # state 2: *11
    result = 0
    state = 0
    count = 0
    b = bin(int(n))[2:]
    for c in bin(int(n))[:1:-1]:
        if c == '0':
            if state == 0: # 0*
                count += 1
            elif state == 1: # 01
                result += 1 + 2 # remove one, divide by 2 twice
                count = 0
                state = 0 # .*01 => .*00 => .*
            elif state == 2: # 01*
                result += 1 + count # add one, divide by 2 count times
                count = 1
                state = 1 # .*01* => .*10* => .*1
        if c == '1':
            if state == 0: # 10*
                result += count # divide by 2 count times
                count = 1
                state = 1 # .*10* => .*1
            elif state == 1: # 11
                count += 1
                state = 2
            elif state == 2: # 1*
                count += 1
    if state == 2: # 11*
        if count == 2: # 11
            result += 2
        else:
            result += 1 + count # add one, devide by 2 count times
    return result


tests = [
        ('15', 5),
        ('4', 2),
        (str(int('1', 2)), 0),
        (str(int('10', 2)), 1),
        (str(int('11', 2)), 2),
        (str(int('100', 2)), 2),
        (str(int('101', 2)), 3),
        (str(int('110', 2)), 3),
        (str(int('111', 2)), 4),
        (str(int('1000', 2)), 3),
        (str(int('1001', 2)), 4),
        (str(int('1010', 2)), 4),
        (str(int('1011', 2)), 6),
        (str(int('1100', 2)), 4),
        (str(int('1101', 2)), 5),
        (str(int('1110', 2)), 5),
        (str(int('1111', 2)), 5),
        (str(int('10001', 2)), 5),
        (str(int('111110', 2)), 7),
        (str(int('101111', 2)), 7),
        (str(int('1101111', 2)), 9),
        (str(int('10001000', 2)), 8),
        (str(int('11001100', 2)), 10),
        (str(int('10101010', 2)), 10),
        (str(int('11011000', 2)), 10),
        (str(int('10000000', 2)), 7),
        ]

for i, o in tests:
    result = solution(i)
    print (i, result == o, result, o)