Merkkijono

x = int(input())
aakkoset = ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o",
            "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z", "å", "ä", "ö"]

# Seuraavalla rivillä on, noh, monia parillisia numeroita.
# Ne on generoitu koodirivillä list(range(0,500,2)).
# Teen sen näin saadakseni koodin suoritusnopeutta leikattua...
parilliset = [0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 102, 104, 106, 108, 110, 112, 114, 116, 118, 120, 122, 124, 126, 128, 130, 132, 134, 136, 138, 140, 142, 144, 146, 148, 150, 152, 154, 156, 158, 160, 162, 164, 166, 168, 170, 172, 174, 176, 178, 180, 182, 184, 186, 188, 190, 192, 194, 196, 198, 200]
merkkijono = []
for a in range(x):
    if a == 0:
        merkkijono.append("a")
    else:
        for b in range(len(merkkijono)):
            merkkijono.insert(parilliset[b], aakkoset[a])
merkkijono_loppu = merkkijono
merkkijono_loppu.reverse()
merkkijono = merkkijono + merkkijono_loppu
merkkijono.remove("a")
print("".join(merkkijono))

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: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 15, in <module>
    merkki...

Test 10

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 15, in <module>
    merkki...

Test 11

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 15, in <module>
    merkki...

Test 12

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 15, in <module>
    merkki...

Test 13

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 15, in <module>
    merkki...

Test 14

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 15, in <module>
    merkki...

Test 15

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 15, in <module>
    merkki...

Test 16

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 15, in <module>
    merkki...