Buggy python submission (verdict: Runtime Error):
def base_convert(nl, ibase, obase):
    o = []
    while any(nl):
        c = 0
        for i in range(len(nl)):
            c = c * ibase + nl[i]
            nl[i],c = divmod(c,obase)
        o.append(c)
    o.reverse()
    return o

def convertList(lst):
    rev_lst = list(reversed(lst))
    for i,num in enumerate(rev_lst):
        if i < len(rev_lst)-1:
            if num <= 0:
                rev_lst[i+1] = rev_lst[i+1]-1
                rev_lst[i] = rev_lst[i] + 26
    return list(reversed(rev_lst))

N = input()
N = list(map(int,[i for i in N]))
lst = base_convert(N,10,26)
lst_converted = convertList(lst)
ans = ''.join([dict1[i] for i in lst_converted])
print(ans)

Fixed submission:
def base_convert(nl, ibase, obase):
    o = []
    while any(nl):
        c = 0
        for i in range(len(nl)):
            c = c * ibase + nl[i]
            nl[i],c = divmod(c,obase)
        o.append(c)
    o.reverse()
    return o

def convertList(lst):
    rev_lst = list(reversed(lst))
    for i,num in enumerate(rev_lst):
        if i < len(rev_lst)-1:
            if num <= 0:
                rev_lst[i+1] = rev_lst[i+1]-1
                rev_lst[i] = rev_lst[i] + 26
    return list(reversed(rev_lst))

dict1 = {
    0: '',
    1: 'a',
    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',
    17: 'q',
    18: 'r',
    19: 's',
    20: 't',
    21: 'u',
    22: 'v',
    23: 'w',
    24: 'x',
    25: 'y',
    26: 'z'
}

N = input()
N = list(map(int,[i for i in N]))
lst = base_convert(N,10,26)
lst_converted = convertList(lst)
ans = ''.join([dict1[i] for i in lst_converted])
print(ans)

Buggy python submission (verdict: Runtime Error):
N = input()
N = list(map(int,[i for i in N]))
lst = base_convert(N,10,26)
lst_converted = convertList(lst)
print(''.join([dict1[i] for i in lst_converted]))

Fixed submission:
def base_convert(nl, ibase, obase):
    o = []
    while any(nl):
        c = 0
        for i in range(len(nl)):
            c = c * ibase + nl[i]
            nl[i],c = divmod(c,obase)
        o.append(c)
    o.reverse()
    return o

def convertList(lst):
    rev_lst = list(reversed(lst))
    for i,num in enumerate(rev_lst):
        if i < len(rev_lst)-1:
            if num <= 0:
                rev_lst[i+1] = rev_lst[i+1]-1
                rev_lst[i] = rev_lst[i] + 26
    return list(reversed(rev_lst))

dict1 = {
    0: '',
    1: 'a',
    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',
    17: 'q',
    18: 'r',
    19: 's',
    20: 't',
    21: 'u',
    22: 'v',
    23: 'w',
    24: 'x',
    25: 'y',
    26: 'z'
}

N = input()
N = list(map(int,[i for i in N]))
lst = base_convert(N,10,26)
lst_converted = convertList(lst)
ans = ''.join([dict1[i] for i in lst_converted])
print(ans)

Buggy python submission (verdict: Runtime Error):
N = input()
N = list(map(int,[i for i in N]))
lst = base_convert(N,10,26)
lst_converted = convertList(lst)
print(''.join([dict1[i] for i in lst_converted]))

Fixed submission:
def base_convert(nl, ibase, obase):
    o = []
    while any(nl):
        c = 0
        for i in range(len(nl)):
            c = c * ibase + nl[i]
            nl[i],c = divmod(c,obase)
        o.append(c)
    o.reverse()
    return o

def convertList(lst):
    rev_lst = list(reversed(lst))
    for i,num in enumerate(rev_lst):
        if i < len(rev_lst)-1:
            if num <= 0:
                rev_lst[i+1] = rev_lst[i+1]-1
                rev_lst[i] = rev_lst[i] + 26
    return list(reversed(rev_lst))

dict1 = {
    0: '',
    1: 'a',
    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',
    17: 'q',
    18: 'r',
    19: 's',
    20: 't',
    21: 'u',
    22: 'v',
    23: 'w',
    24: 'x',
    25: 'y',
    26: 'z'
}

N = input()
N = list(map(int,[i for i in N]))
lst = base_convert(N,10,26)
lst_converted = convertList(lst)
ans = ''.join([dict1[i] for i in lst_converted])
print(ans)

Buggy python submission (verdict: Runtime Error):
N = input()
N = list(map(int,[i for i in N]))
lst = base_convert(N,10,26)
lst_converted = convertList(lst)
print(''.join([dict1[i] for i in lst]))

Fixed submission:
def base_convert(nl, ibase, obase):
    o = []
    while any(nl):
        c = 0
        for i in range(len(nl)):
            c = c * ibase + nl[i]
            nl[i],c = divmod(c,obase)
        o.append(c)
    o.reverse()
    return o

def convertList(lst):
    rev_lst = list(reversed(lst))
    for i,num in enumerate(rev_lst):
        if i < len(rev_lst)-1:
            if num <= 0:
                rev_lst[i+1] = rev_lst[i+1]-1
                rev_lst[i] = rev_lst[i] + 26
    return list(reversed(rev_lst))

dict1 = {
    0: '',
    1: 'a',
    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',
    17: 'q',
    18: 'r',
    19: 's',
    20: 't',
    21: 'u',
    22: 'v',
    23: 'w',
    24: 'x',
    25: 'y',
    26: 'z'
}

N = input()
N = list(map(int,[i for i in N]))
lst = base_convert(N,10,26)
lst_converted = convertList(lst)
ans = ''.join([dict1[i] for i in lst_converted])
print(ans)