alist = [12,15,20,17,9,13,8,6]

n = len (alist)

for i in range(0,n-1):
    for j in range(0,n-1):

        if alist[j] > alist[j + 1]:
            alist[j],alist[j + 1] = alist[j + 1], alist[j]
print(alist)