Buggy python submission (verdict: Runtime Error):
N = int(input())
q = [0]*12
i = 10
n = N
cflag = 0
str = []
while i != -1:
    q[i] = n // 26 ** i
    mod = n % 26 ** i
    n = mod
    i -= 1
for i in range(12):
    if q[i] == 0 and q[i+1] == 0:
        break
    elif q[i] == 0:
        str.append("z")
        cflag = 1
    elif q[i] == 1 and q[i+1] == 0 and cflag == 1:
        break
    elif q[i] == 1 and cflag == 1:
        str.append ("z")
    else:
        str.append(chr(q[i] + 96 -cflag))
        cflag = 0

i = len(str) -1
while i >= 0:
    if[str] == '':
        i-=1
        continue
    elif i == 0:
        print(str[i])
        break
    else:
        print(str[i], end="")
        i -= 1


Fixed submission:
N = int(input())
q = [0]*13
i = 10
n = N
cflag = 0
zflag = 0
str = []
while i != -1:
    q[i] = n // 26 ** i
    mod = n % 26 ** i
    n = mod
    i -= 1
for i in range(12):
    if q[i] == 0:
        zflag = 1
        for j in range(i,13) :
            if q[j] != 0:
                zflag = 0
                break
        if zflag == 1:
             break
        elif cflag == 1:
            str.append("y")
            cflag = 1
        else:
            str.append("z")
            cflag = 1
    elif q[i] == 1 and cflag == 1:
        zflag = 1
        for j in range(i+1,13):
            if q[j] != 0:
                zflag = 0
                break
        if zflag == 1:
            break
        else:
            str.append ("z")
            cflag = 1
    else:
        str.append(chr(q[i] + 96 -cflag))
        cflag = 0

i = len(str) -1
while i >= 0:
    if[str] == '':
        i-=1
        continue
    elif i == 0:
        print(str[i])
        break
    else:
        print(str[i], end="")
        i -= 1

Buggy python submission (verdict: Runtime Error):
N = int(input())
q = [0]*11
i = 10
n = N
cflag = 0
str = []
while i != -1:
    q[i] = n // 26 ** i
    mod = n % 26 ** i
    n = mod
    i -= 1
for i in range(11):
    if q[i] == 0 and q[i+1] == 0:
        break
    elif q[i] == 0:
        str.append("z")
        cflag = 1
    elif q[i] == 1 and q[i+1] == 0 and cflag == 1:
        break
    elif q[i] == 1 and cflag == 1:
        str.append ("z")
    else:
        str.append(chr(q[i] + 96 -cflag))
        cflag = 0

i = len(str) -1
while i >= 0:
    if[str] == '':
        i-=1
        continue
    elif i == 0:
        print(str[i])
        break
    else:
        print(str[i], end="")
        i -= 1



Fixed submission:
N = int(input())
q = [0]*13
i = 10
n = N
cflag = 0
zflag = 0
str = []
while i != -1:
    q[i] = n // 26 ** i
    mod = n % 26 ** i
    n = mod
    i -= 1
for i in range(12):
    if q[i] == 0:
        zflag = 1
        for j in range(i,13) :
            if q[j] != 0:
                zflag = 0
                break
        if zflag == 1:
             break
        elif cflag == 1:
            str.append("y")
            cflag = 1
        else:
            str.append("z")
            cflag = 1
    elif q[i] == 1 and cflag == 1:
        zflag = 1
        for j in range(i+1,13):
            if q[j] != 0:
                zflag = 0
                break
        if zflag == 1:
            break
        else:
            str.append ("z")
            cflag = 1
    else:
        str.append(chr(q[i] + 96 -cflag))
        cflag = 0

i = len(str) -1
while i >= 0:
    if[str] == '':
        i-=1
        continue
    elif i == 0:
        print(str[i])
        break
    else:
        print(str[i], end="")
        i -= 1