def max_sequence(arr):
    totalmax = 0
    currentmax = 0
    
    for i in arr:
        currentmax += i
        
        if totalmax < currentmax:
            totalmax = currentmax
        if currentmax < 0:
            currentmax = 0
            
    return totalmax

def count_positives_sum_negatives(arr):
    if len(arr) == 0:
        return arr
    
    sum = 0
    count = 0
    for i in arr:
        if i > 0:
            count += 1
        if i < 0:
            sum += i

    return [count, sum]

def count_positives_sum_negatives(arr):
    total = sum(i for i in arr if i < 0)
    count = sum(1 for i in arr if i > 0)
    return [count, total] if len(arr) else []

def tower_builder(n_floors):
    tower = []
    space = (n_floors * 2) - 1
    for i in range(n_floors):
        sign = '*' * ((i * 2) + 1)
        floor = sign.center(space)
        tower.append(floor)
    return tower

def tower_builder(n_floors):
    space = (n_floors * 2) - 1
    return [('x' * ((i * 2) + 1)).center(space) for i in range(n_floors)]

def is_triangle(a, b, c):
    if (a + b > c) and (a + c > b) and (b + c > a):
        return True
    else:
        return False

def nb_year(p0, percent, aug, p):
    totalp = 0
    year = 0
    percent = percent / 100
    while totalp < p:
        totalp = p0 + (p0 * percent) + aug
        totalp = int(totalp)
        p0 = totalp
        year += 1
    return year 

namelist([ {'name': 'Bart'}, {'name': 'Lisa'}, {'name': 'Maggie'} ])
# returns 'Bart, Lisa & Maggie'

namelist([ {'name': 'Bart'}, {'name': 'Lisa'} ])
# returns 'Bart & Lisa'

namelist([ {'name': 'Bart'} ])
# returns 'Bart'

namelist([])
# returns ''

def namelist(names):
    lnames = [name['name'] for name in names] #Unpack name values from dictionary into a list
    flist = lnames[:-2] #flist of names exluding last two elements
    elist = lnames[-2:] #elist containing last two elements
    eString = ' & '.join(elist) #string of last two elements joined with '&'

    if len(lnames) <= 1:
        return ''.join(lnames) #returns single element as string
    else:
        nflist = [name + ',' for name in flist] #create nflist containing comma modified elements from flist
        nflist.append(eString) #added last string as an element to nflist
        return ' '.join(nflist) #returns list elements as strings

a = ['Seun','Mike','Samson','John','Wayne']
j = ''
for i in a:
    j = j + a.pop()
    j += ', '
print(j)