Merkkijono

# Online Python compiler (interpreter) to run Python online.
# Write Python 3 code in this online editor and run it.
n=int(input())-1
alp="bcdefghijklmnop"
s="a"
os=""
for i in range(0, n):
    a=alp[i]
    os += a
    for c in s:
        os += c + a
    s=os
    os=""

print(s)

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