Merkkijono

def main():
    string = ["a"]
    n = int(input())

    if n == 1:
        print("a")
        return

    alphabet = {
        2: "b",
        3: "c",
        4: "d",
        5: "e",
        6: "f",
        7: "g",
        8: "h",
        9: "i",
        10: "j",
        11: "k",
        12: "l",
        13: "m",
        14: "n",
        15: "o",
        16: "p"
    }

    for i in range(2, n+1):
        for j in range(2**(i-1)):
            string.insert(j*2, alphabet[i])

    output = ""

    for item in string:
        output += item

    print(output)
    return


main()

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