Merkkijono

list = ["a"]
alphabet_list = ["b","c","d","e","f","g","h","i","j","k","l","m","n","o","p"]
n = int(input())
i = 2  #lisättävien kirjainten määrä
c = 0  #kertoo mikä kirjain lisätään
while n > 1:  #toistetaan kunnes n on 1
    b = 0 #kertoo mihin väliin lisätään kirjain
    while b < i: # toistetaan kunnes on lisätty riittävän monta kirjainta
        list.insert((b*2), alphabet_list[c])
        b += 1
    i = 2 * i
    n -=1
    c += 1
string = ""
for letter in list:
    string += letter
print(string)

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED