Buggy python submission (verdict: Runtime Error):
def main():
    n = int(input())
    alphabet = ['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']
    #print(len(alphabet))
    ans = ''
    
    i = 1
    length = 1
    while (26 ** (i-1)) + (26 ** i) < n:
        length += 1
        i += 1
        #print(length)
    
    #print(length)
    for j in reversed(range(1, length+1)):
        r = n // 26 **(j-1)
        n -= (26 ** (j - 1))* r
        ans = alphabet[r-1] + ans
        #print(j)
    
    
    print(ans)
    
if __name__ == '__main__':
    main()

Fixed submission:

def main():
    n = int(input())
    ans = ''
    
    for i in range(1, 99):
        if n <= 26 ** i:
            n -= 1
            for j in range(i):
                ans += chr(ord('a') + n % 26)
                n //= 26
            break
        else:
            n -= 26 ** i
    
    print(ans[::-1])
    
if __name__ == '__main__':
    main()

Buggy python submission (verdict: Runtime Error):

def main():
    n = int(input())
    alphabet = ['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']
    #print(len(alphabet))
    exponent_list = [0]
    for i in range(1, 12):
        exponent_list.append(exponent_list[i-1] + 26**i)
    #print(exponent_list)
    index = 0
    n_index = 0
    ans = ''
    

    
    while exponent_list[index] < n:
        n_index = index
        index += 1
    #print(n_index)
    r_list = []
    r = 27
    b = 0
    while r > 27:
        tmp = n - exponent_list[n_index]
        r = int(tmp/26)
        b = tmp % 26
    
    ans = alphabet[r] + alphabet[b]
    print(ans)
    
if __name__ == '__main__':
    main()

Fixed submission:

def main():
    n = int(input())
    ans = ''
    
    for i in range(1, 99):
        if n <= 26 ** i:
            n -= 1
            for j in range(i):
                ans += chr(ord('a') + n % 26)
                n //= 26
            break
        else:
            n -= 26 ** i
    
    print(ans[::-1])
    
if __name__ == '__main__':
    main()

Buggy python submission (verdict: Runtime Error):

def main():
    n = int(input())
    alphabet = ['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']
    #print(len(alphabet))
    exponent_list = [0]
    for i in range(1, 12):
        exponent_list.append(exponent_list[i-1] + 26**i)
    #print(exponent_list)
    index = 0
    n_index = 0
    ans = ''
    

    
    while exponent_list[index] < n:
        n_index = index
        index += 1
    #print(n_index)
    r_list = []
    r = 27
    b = 0
    while r > 27:
        tmp = n - exponent_list[n_index]
        r = int(tmp/26)
        b = tmp % 26
    
    ans = alphabet[r] + alphabet[b]
    print(ans)
    
if __name__ == '__main__':
    main()

Fixed submission:

def main():
    n = int(input())
    ans = ''
    
    for i in range(1, 99):
        if n <= 26 ** i:
            n -= 1
            for j in range(i):
                ans += chr(ord('a') + n % 26)
                n //= 26
            break
        else:
            n -= 26 ** i
    
    print(ans[::-1])
    
if __name__ == '__main__':
    main()