Problem:


Score : 200 points

Problem Statement

You are given a string S consisting of lowercase English letters.
Find the lexicographically (alphabetically) smallest lowercase English letter that does not occur in S.
If every lowercase English letter occurs in S, print None instead.

Constraints

1 \leq |S| \leq 10^5 (|S| is the length of string S.)

S consists of lowercase English letters.

Input

Input is given from Standard Input in the following format:

S

Output

Print the lexicographically smallest lowercase English letter that does not occur in S.
If every lowercase English letter occurs in S, print None instead.

Sample Input 1

atcoderregularcontest

Sample Output 1

b

The string atcoderregularcontest contains a, but does not contain b.

Sample Input 2

abcdefghijklmnopqrstuvwxyz

Sample Output 2

None

This string contains every lowercase English letter.

Sample Input 3

fajsonlslfepbjtsaayxbymeskptcumtwrmkkinjxnnucagfrg

Sample Output 3

d



Sample input:
atcoderregularcontest


Sample output:
b

Submission status: Accepted

Solution code:
from string import ascii_lowercase
alpha = {i for i in ascii_lowercase}
s = set([i for i in input()])
ans = sorted(alpha - s)
if ans==[]:
    print('None')
else:
    print(ans[0])

Submission status: Accepted

Solution code:
s = input()
sample = list("abcdefghijklmnopqrstuvwxyz")

for i in s:
    if i in sample:
        sample.remove(i)

if len(sample) == 0:
    print("None")
else:
    print(sample[0])

Submission status: Accepted

Solution code:
from string import ascii_lowercase

s = set(list(input()))

for c in ascii_lowercase:
    if c not in s:
        print(c)
        exit()
print("None")

Submission status: Accepted

Solution code:
S = list(input())
S = list(set(S))
allset = [chr(i) for i in range(97, 97+26)]
not_duplicate = list(set(allset) ^ set(S))
not_duplicate.sort()
print(not_duplicate[0]) if len(not_duplicate) != 0 else print("None")

Submission status: Accepted

Solution code:
import sys
input = sys.stdin.readline
s = input()

chrs = [chr(i) for i in range(97, 97+26)]

for i in chrs:
  if i not in s:
    print(i)
    exit()
print("None")

Submission status: Accepted

Solution code:
key = ["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", "None"]
judge = dict()
for value in key:
  judge[value] = False
s = input()
n = len(s)
for i in range(n):
  judge[s[i]] = True

for i in range(27):
  if judge[key[i]] == False:
    print(key[i])
    break

Submission status: Accepted

Solution code:
mset=set(list(input()))
aset=set(list("qazwsxedcrfvtgbyhnujmikolp"))
aset=aset-mset
lis=sorted(list(aset))
if len(lis):
    print(lis[0])
else:
    print("None")

Submission status: Accepted

Solution code:
s = input()
l = list({s[i] for i in range(len(s))})
a = [False] * 26
for c in l:
    a[ord(c) - ord("a")] = True
ans = "None"
for i in range(len(a)):
    if a[i] == False:
        ans = chr(ord("a") + i)
        break
print(ans)

Submission status: Accepted

Solution code:
import string


S = input()
lowercase_list = string.ascii_lowercase

bucket = [0 for i in range(len(lowercase_list))]
for s_i in S:
    bucket[lowercase_list.index(s_i)] += 1


for index, val in enumerate(bucket):
    if val == 0:
        print(lowercase_list[index])
        exit()
print('None')

Submission status: Accepted

Solution code:
s = input()
flg = 0
for i in 'abcdefghijklmnopqrstuvwxyz':
    if i not in s:
        print(i)
        flg = 1
        break
if flg == 0:
    print('None')

Submission status: Accepted

Solution code:
s = input()
alps = 'abcdefghijklmnopqrstuvwxyz'
for i in alps:
    if i not in s:
        print(i)
        break
else:
    print('None')

Submission status: Accepted

Solution code:
s = input()
alps = 'abcdefghijklmnopqrstuvwxyz'
for alp in alps:
    if alp not in s:
        print(alp)
        break
else:
    print('None')

Submission status: Accepted

Solution code:
icase=0
if icase==0:
    s=set(input())
    abc=list("abcdefghijklmnopqrstuvwxyz")
#    abc.sort(reverse=True)
    yn=""
    for i in range(len(abc)):
        if not abc[i] in s:
            print(abc[i])
            yn="OK"
            break
    if yn=="":
        print("None")

Submission status: Accepted

Solution code:
import itertools
import math
import string
import collections
from collections import Counter
from collections import deque
import sys
sys.setrecursionlimit(2*10**5)
INF = 2**60


def readints():
    return list(map(int, input().split()))


def nCr(n, r):
    return math.factorial(n)//(math.factorial(n-r)*math.factorial(r))


def has_duplicates2(seq):
    seen = []
    for item in seq:
        if not(item in seen):
            seen.append(item)
    return len(seq) != len(seen)


def divisor(n):
    divisor = []
    for i in range(1, n+1):
        if n % i == 0:
            divisor.append(i)
    return divisor


# coordinates
dx = [-1, -1, -1, 0, 0, 1, 1, 1]
dy = [-1, 0, 1, -1, 1, -1, 0, 1]

S = input()
#print('S', S)
SS = list(S)
a = []
for i in range(97, 97+26):
    a.append(chr(i))

result = list(set(a)-set(SS))
#print('seta', set(a))
#print('setSS', set(SS))
# print(result)
if result == []:
    print('None')
else:
    print(sorted(result)[0])

Submission status: Accepted

Solution code:
import sys
S = input()
als = ["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"]

for i in range(len(S)):
    if S[i] in als:
        als.remove(S[i])
    if als ==[]:
        print("None")
        sys.exit()
print(als[0])

Submission status: Accepted

Solution code:
eng=['a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','x','y','z']

sentence=input()
sentence= sentence.lower()

for i in eng:
  if not i in sorted(list(set(sorted(sentence)))):
    print(i)
    break
else:
    print('None')

Submission status: Accepted

Solution code:
S = list(input())
s = set(S)

A ={"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"}

ans = A - s

ANS = list(ans)

ANS.sort()

if ANS != []:
    print(ANS[0])
else:
    print("None")

Submission status: Accepted

Solution code:
# solution
import io

data=input()

for i in 'abcdefghijklmnopqrstuvwxyz':
    if not i in data:
        print(i)
        break
else:
    print('None')

Submission status: Accepted

Solution code:
# from math import factorial,sqrt,ceil,gcd
# from itertools import permutations as permus
# from collections import deque,Counter
# import re
# from decimal import Decimal, getcontext
# # getcontext().prec = 1000
# # eps = Decimal(10) ** (-100)

# import numpy as np
# from scipy.sparse.csgraph import shortest_path, dijkstra, floyd_warshall, bellman_ford, johnson
# from scipy.sparse import csr_matrix

slist = "abcdefghijklmnopqrstuvwxyz"
S = input()

fulset = set(list(slist))
Sset = set(list(S))
kouho = fulset-Sset

ans = "None"
if len(kouho)!=0:
    ans = min(kouho)
print(ans)
# print(*ans)   # unpackして出力。間にスペースが入る
# for row in board:
#     print(*row,sep="")    #unpackして間にスペース入れずに出力する
# print("{:.10f}".format(ans))
# print("{:0=10d}".format(ans))

Submission status: Accepted

Solution code:
from string import ascii_lowercase

s = input()
for c in ascii_lowercase:
    if c not in s:
        print(c)
        break
else:
    print('None')

Submission status: Accepted

Solution code:

s = list(input())

for i in range(97,123):
    if chr(i) not in s:
        print(chr(i))
        exit()
print("None")

Submission status: Accepted

Solution code:
s=input()
al=[chr(_) for _ in range(97,123)]
for i in range(len(s)):
    if s[i] in al:
        al.remove(s[i])
if len(al)==0:
    print('None')
else:
    print(al[0])

Submission status: Accepted

Solution code:
s=input()
s=list(set(s))

A=[]
for i in range(97,123):
    A.append(chr(i))


for i in range(len(A)):
    if A[i] in s:
        continue
    else:
        print(A[i])
        exit()

print("None")

Submission status: Accepted

Solution code:
s = list(input())
label = [chr(i) for i in range(97, 97+26)]

ans = "None"
for l in label:
  if not l in s:
    ans = l
    break
    
print(ans)

Submission status: Accepted

Solution code:
s=input()
s=list(set(s))

A=[]
for i in range(97,123):
    A.append(chr(i))


for i in range(len(A)):
    if A[i] in s:
        continue
    else:
        print(A[i])
        exit()

print("None")

Submission status: Accepted

Solution code:
s = list(input())
flag = True
# ord(文字) == 文字を表す整数(ASCIIコード)
# chr(整数) == 整数に対応する文字
for i in range(ord('a'), ord('z') + 1):
    if s.count(chr(i)) == 0:
        flag = False
        ans = chr(i)
        break
print('None' if flag else ans)

Submission status: Accepted

Solution code:
S = input()
alpha = [chr(ord("a") + i) for i in range(26)]

for a in alpha:
    if a not in S:
        print(a)
        break
else:
    print("None")

Submission status: Accepted

Solution code:
def main():
    S = input()
    alphabet = "abcdefghijklmnopqrstuvwxyz"
    flag = 0
    for c in alphabet:
        if S.count(c) == 0:
            print(c)
            flag = 1
            break
    if flag == 0:
        print("None")
main()

Submission status: Accepted

Solution code:
s = set('abcdefghijklmnopqrstuvwxyz')
S = input()

for c in S:
    if c in s:
        s.remove(c)

if len(s) == 0:
    print('None')
else:
    print(min(s))

Submission status: Accepted

Solution code:
S = input()

for i in range(27):
  if i == 26:
    print("None")
  elif chr(i+97) in S:
    continue
  else:
    print(chr(i+97))
    break

Submission status: Accepted

Solution code:
S = set(list(input()))
b = set(list("abcdefghijklmnopqrstuvwxyz"))

if len(S) == 26:
  print("None")
else:
  print(sorted(list(b-S))[0])

Submission status: Accepted

Solution code:
S = input()
al = [chr(i) for i in range(97, 97+26)]

for i in al:
    if i not in S:
        print(i)
        exit()


print('None')

Submission status: Accepted

Solution code:
S = input()

s = set(S)

if len(s) == 26:
    print('None')
else:
    for i in 'abcdefghijklmnopqrstuvwxyz':
        if i not in S:
            print(i)
            break

Submission status: Accepted

Solution code:
def myAnswer(S:set)-> str:
   alf = [chr(ord('a')+i) for i in range(26)]
   counter = "None"
   for a in alf:
      if((a in S) == False):
         counter=a
         break
   return counter



   

def modelAnswer():
   tmp=1
def main():
   S = set(input())
   print(myAnswer(S))

if __name__ == '__main__':
   main()

Submission status: Accepted

Solution code:
S = input()

for i in range(ord('a'), ord('a') + 26):
    if chr(i) not in S:
        print(chr(i))
        break
else:
    print('None')

Submission status: Accepted

Solution code:
s = input()
Al = [chr(_)  for _ in range(97,123)]
   
for i in range(len(s)):
  if s[i] in Al:
    Al.remove(s[i])

if len(Al) ==0:
    print('None')
else :
    print(Al[0])

Submission status: Accepted

Solution code:
import collections

S =input()
char = collections.Counter(S)
char_bas = 'abcdefghijklmnopqrstuvwxyz'

for i in range(len(char_bas)):
    if char_bas[i] in char:
        if char_bas[i] == 'z':
            print('None')
            break
        continue
    else:
        print(char_bas[i])
        break

Submission status: Accepted

Solution code:
# ABC 071: B – Not Found
a = 'abcdefghijklmnopqrstuvwxyz'
s = input()
for c in s:
    if c in a:
        a = a.replace(c, '')

print(a[0] if len(a) > 0 else 'None')

Submission status: Accepted

Solution code:
S = set(input())
ascii_list = [i for i in range(97, 123)]
for i in S:
    ascii_list.remove(int(ord(i)))
if ascii_list:
    print(chr(ascii_list[0]))
else:
    print('None')

Submission status: Accepted

Solution code:
import string


def main():
    s = input()
    a = {i: False for i in string.ascii_lowercase}
    for i in s:
        a[i] = True
    r = [i for i, j in a.items() if j == False]
    if 0 < len(r):
        print(r[0])
    else:
        print("None")


main()

Submission status: Accepted

Solution code:
S = input()

word = 'abcddefghijklmnopqrstuvwxyz'

import sys

for s in word:
    if S.count(s) == 0:
        print(s)
        sys.exit()
        
print('None')

Submission status: Accepted

Solution code:
S = input()
a = set([chr(i) for i in range(ord('a'),ord('a')+26)])
S = set(list(S))
A = a-S
if len(A)==0:
    print('None')
else:
    print(sorted(list(A))[0])

Submission status: Accepted

Solution code:
S = input()
L = "abcdefghijklmnopqrstuvwxyz"
for i in L:
  if i not in S:
    print(i)
    exit()
print("None")

Submission status: Accepted

Solution code:
s = input()
a = True
for i in range(97,123):
    if not(chr(i) in s):
        print(chr(i))
        a = False
        break
if a:
    print(None)

Submission status: Accepted

Solution code:
import collections
import sys
import numpy as np
sys.setrecursionlimit(1000000000)
from heapq import heapify,heappop,heappush,heappushpop
MOD = 10**9+7
import itertools
import math

s = input()
li = ["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"]
li_cnt = [0]*26
for i in range(len(s)):
    for j in range(len(li)):
        if li[j] == s[i]:
            li_cnt[j] += 1
ans = ""
for i in range(len(li_cnt)):
    if li_cnt[i] == 0:
        ans += li[i]
        break
if len(ans) == 0:
    print("None")
else:
    print(ans)

Submission status: Accepted

Solution code:
import string

s = set(input())

a = set(string.ascii_lowercase)
b = sorted(list(a - s))
ans = b[0] if len(b) else "None"
print(ans)

Submission status: Accepted

Solution code:
S = input()

used = set([s for s in S])
ans = "None"
for c in [chr(i) for i in range(97, 97 + 26)]:
    if c not in used:
        ans = c
        break

print(ans)

Submission status: Accepted

Solution code:
s  =input()
alp = [chr(ord('a')+i)for i in range(26)]
for x in alp:
    if x not in s:
        print(x)
        exit(0)
print('None')

Submission status: Accepted

Solution code:
S = list(input())
S = set([ord(s) for s in S])

for i in range(97, 123):
    if i not in S:
        print(chr(i))
        exit()
else:
    print('None')

Submission status: Accepted

Solution code:
alphabets = "abcdefghijklmnopqrstuvwxyz"


s = input()

FOUND = {c:False for c in alphabets}
for c in s:
    FOUND[c] = True

for c in alphabets:
    if not FOUND[c]:
        print(c)
        exit()
print(None)

Submission status: Accepted

Solution code:
import string
s = set(list(input()))
ans = 'None'
for c in string.ascii_lowercase:
    if not c in s:
        ans = c
        break

print(ans)

Submission status: Accepted

Solution code:
from __future__ import print_function

import sys

import re
import array
import copy
import functools
import operator

import math
import string
import fractions
from fractions import Fraction
from fractions import gcd
# fractions.gcd() を用いること
# math.log2()はatcoderでは対応していない．留意せよ．

import collections
import itertools
import bisect

import random
import time

import heapq
from heapq import heappush
from heapq import heappop
from heapq import heappushpop
from heapq import heapify
from heapq import heapreplace
from queue import PriorityQueue as pq
from queue import Queue

from itertools import accumulate

from collections import deque
from collections import Counter

from operator import mul
from functools import reduce

input = sys.stdin.readline


def eprint(*args, **kwargs):
    print(*args, file=sys.stderr, **kwargs)
    return


def lcm(n, m):
    return int(n * m / gcd(n, m))


def coprimize(p, q):
    common = fractions.gcd(p, q)
    return (p // common, q // common)


def combinations_count(n, r):
    r = min(r, n - r)
    numer = reduce(mul, range(n, n - r, -1), 1)
    denom = reduce(mul, range(1, r + 1), 1)
    return numer // denom


def find_gcd(list_l):
    x = reduce(gcd, list_l)
    return x


def main():
    S = set(list("abcdefghijklmnopqrstuvwxyz")) - set(list(input().strip())) 
    if len(list(S))!=0:
        print( sorted(list(S))[0] )
    else:
        print("None")
    

if __name__ == '__main__':
    main()

Submission status: Accepted

Solution code:
alphabet = [chr(ord('a') + i) for i in range(26)]
s = list(input())
s = sorted(list(set(s)))
if len(s) == 26:
    print("None")
    exit()
for i in range(len(s)):
    if i == len(s) - 1:
        if s[i] == alphabet[i]:
            print(alphabet[i+1])
        else:
            print(alphabet[i])
        exit()
    if s[i] == alphabet[i]:
        pass
    else:
        print(alphabet[i])
        exit()

Submission status: Accepted

Solution code:
alphabet = [chr(ord('a') + i) for i in range(26)]
s = list(input())
s = sorted(list(set(s)))
if len(s) == 26:
    print("None")
    exit()
for i in range(len(s)):
    if s[i] == alphabet[i]:
        pass
    else:
        print(alphabet[i])
        exit()
print(alphabet[i+1])
exit()

Submission status: Accepted

Solution code:
s = input()

dicts = {i: False for i in range(ord('a'), ord('z') + 1)}

for i in s:
    if not dicts[ord(i)]:
        dicts[ord(i)] = True

for i in range(ord('a'), ord('z') + 1):
    if not dicts[i]:
        print(chr(i))
        exit()
print('None')

Submission status: Accepted

Solution code:
list_N = set(input())
lower_cha = set([chr(ord('a') + i) for i in range(26)])

ans = list(lower_cha-list_N)
ans.sort()
if len(ans) == 0:
    print("None")
else:
    print(ans[0])

Submission status: Accepted

Solution code:
d=set(input())
s="".join(sorted(list(d)))
for i in range(26):
    if chr(ord("a")+i) not in d:print(chr(ord("a")+i));break
else:print("None")

Submission status: Accepted

Solution code:
s=input()
al = list('abcdefghijklmnopqrstuvwxyz')
for s0 in s:
    if s0 in al:
        al.remove(s0)
if len(al) == 0:
    print(None)
else:
    print(al[0])

Submission status: Accepted

Solution code:
s = str(input())
S = [s[i] for i in range(len(s))]
S.sort()
S = set(S)
fr = 0
count = [chr(i) for i in range(97, 97+26)]
for i in count:
    if i in S:
        pass
    else:
        print(i)
        fr += 1
        break
if fr == 0:
    print('None')

Submission status: Accepted

Solution code:
import sys
import os

ii = lambda: int(sys.stdin.buffer.readline().rstrip())
il = lambda: list(map(int, sys.stdin.buffer.readline().split()))
fl = lambda: list(map(float, sys.stdin.buffer.readline().split()))
iln = lambda n: [int(sys.stdin.buffer.readline().rstrip()) for _ in range(n)]

iss = lambda: sys.stdin.buffer.readline().decode().rstrip()
sl = lambda: list(map(str, sys.stdin.buffer.readline().decode().split()))
isn = lambda n: [sys.stdin.buffer.readline().decode().rstrip() for _ in range(n)]

MOD = 10 ** 9 + 7


def main():
    if os.getenv("LOCAL"):
        sys.stdin = open("input.txt", "r")

    S = list(iss())
    for n in range(ord('a'), ord('z') + 1):
        if chr(n) not in S:
            print(chr(n))
            exit()
    else:
        print('None')


if __name__ == '__main__':
    main()

Submission status: Accepted

Solution code:
import string
t = list(string.ascii_lowercase)
s = input()

def find(s):
    for i in t:
        if s.count(i) == 0:
            return i
    return 'None'

print(find(s))

Submission status: Accepted

Solution code:
s=input()

sets=set(s)

for i in range(97,123):
  if not chr(i) in sets:
    print(chr(i))
    exit()
print("None")

Submission status: Accepted

Solution code:
s=input()
a=[chr(i) for i in range(ord("a"),ord("z")+1) if chr(i) not in s]
print("None" if len(a)==0 else a[0])

Submission status: Accepted

Solution code:
s=input()
ls=["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"]

for i in range(len(s)):
  if s[i] in ls:
    ls.remove(s[i])
    
if len(ls)>0:
  print(ls[0])
  
else:
  print("None")

Submission status: Accepted

Solution code:
s=list(set(list(input())))
s.sort()
alphabet=list("abcdefghijklmnopqrstuvwxyz")
for i in s:
    alphabet.remove(i)
    
if alphabet==[]:
    print("None")
else:
    print(alphabet[0])

Submission status: Accepted

Solution code:
s=set(list(input()))
a=set([chr(i+97) for i in range(26)])
a-=s
print(sorted(list(a))[0] if len(a)!=0 else "None")

Submission status: Accepted

Solution code:
s=str(input())
ch=[]
for c in 'abcdefghijklmnopqrstuvwxyz':
    ch.append(c)

for c in s:
    if c in ch:
        del ch[ch.index(c)]

ch.sort()
print('None' if len(ch)==0 else ch[0])

Submission status: Accepted

Solution code:
s = list(input())
if len(set(s)) == 26:
    print('None')
else:
    l = 'abcdefghijklmnopqrstuvwxyz'
    for i in l:
        if i in s:
            continue
        else:
            print(i)
            exit()

Submission status: Accepted

Solution code:
import string
print((sorted(set(string.ascii_lowercase)-set(input()))+[None])[0])

Submission status: Accepted

Solution code:
import string
print((sorted(set(string.ascii_lowercase) - set(input())) + ["None"])[0])

Submission status: Accepted

Solution code:
S = list(input())
ans = "None"
alphabets = ["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"]

for item in alphabets:
    if not item in S:
        ans = item
        break

print(ans)

Submission status: Accepted

Solution code:
s = sorted(input())
t=[]
tf = [False]*(97+26+1)


for i in range(len(s)):
  t.append(ord(s[i]))
x=97
for i in set(t):
  tf[i]=True

for i in range(97,97+26):
  if not tf[i]:
    print(chr(i))
    exit()
print("None")

Submission status: Accepted

Solution code:
s = input()

set_s = set(list(s))
x = 'abcdefghijklmnopqrstuvwxyz'

r = None
for i in x:
  if i not in sorted(list(s)) :
    r = i
    break
    
print(r)

Submission status: Accepted

Solution code:
import sys
s = input()
l = "abcdefghijklmnopqrstuvwxyz"
for i in range (len(l)):
    count = 0
    for j in range (len(s)):
        if(l[i] == s[j]):
            count += 1
            break
    if (count == 0):
        print(l[i])
        sys.exit()
print("None")

Submission status: Accepted

Solution code:
S=set(input())
A={"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"}
D=sorted(list(A-S))
if len(D)==0:
  print("None")
else:
  print(D[0])

Submission status: Accepted

Solution code:
s = input()

ans = []

for i in range(ord("a"), ord("z")+1):
    if not chr(i) in s:
        print(chr(i))
        exit()

print("None")

Submission status: Accepted

Solution code:
A = set(list(input()))
a = ord('a')
for i in range(26):
    c = chr(a + i)
    if c not in A:
        ans = c
        break
else:
    ans = 'None'
print(ans)

Submission status: Accepted

Solution code:
s = input()

ans = []

for i in range(ord("a"), ord("z")+1):
    if not chr(i) in s:
        ans.append(chr(i))

if len(ans) == 0:
    print("None")
else:
    print(sorted(ans)[0])

Submission status: Accepted

Solution code:
s = input()
for i in range(ord('a'), ord('z')+1):
    a = chr(i)
    if a not in s:
        print(a)
        break
else:
    print('None')

Submission status: Accepted

Solution code:
s = set(input())
alp = "abcdefghijklmnopqrstuvwxyz"
alpl = [i for i in alp]
for i in s:
    if i in alp:
        alpl.remove(i)
if len(alpl) != 0:        
    print(sorted(alpl)[0])

else:
    print("None")

Submission status: Accepted

Solution code:
import collections
s = input()
s = collections.Counter(s)
alphabet = "abcdefghijklmnopqrstuvwxyz"
for i in alphabet:
  if s[i] == 0:
    print(i)
    exit()
print("None")

Submission status: Accepted

Solution code:
s = str(input())
chars = set([c for c in s])
#print(chars)
ans = 'None'
for i in range(ord('a'), ord('z')+1):
  #print(i, chr(i))
  if chr(i) not in chars:
    ans = chr(i)
    break
print(ans)

Submission status: Accepted

Solution code:
#import itertools
#import fractions
#import numpy as np
#mod = 10**4 + 7
"""def kiri(n,m):
  r_ = n / m
  if (r_ - (n // m)) > 0:
    return (n//m) + 1
  else:
    return (n//m)"""

# Written by NoKnowledgeGG @YlePhan

#import math
#mod = 10**9+7



def main():
  #print(ord('x')) z:122
  #print(ord('a')) a:97
  #print(chr(97)) 97:a
  s = input()
  dic = {}
  for a in s:
    if not a in dic.keys():
      dic[a] = 1
    else:
      pass
  for i in range(97,123):
    if not str(chr(i)) in dic.keys():
      print(chr(i))
      exit()
  print('None')
      
if __name__ == '__main__':
  main()

Submission status: Accepted

Solution code:
s=input()
t=list(chr(i) for i in range(97,97+26))  
bools=True
for i in t:
  if i not in s:
    print(i)
    bools=False
    break
if bools:print("None")

Submission status: Accepted

Solution code:
S = input()


for i in range(97, 123):
    if chr(i) not in S:
        print(chr(i))
        break
else:
    print("None")

Submission status: Accepted

Solution code:

import math
import itertools
import statistics
#import numpy as np
import collections

#n = int(input())
#h, w = list(map(int, input().split()))
s = input()
alf = ["a","b", "c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","i","s","t","u","v","w","x","y","z"]
have = []
for i in range(len(s)):
    for j in range(len(alf)):
        if s[i]==alf[j]:
            have.append(alf[j])

have = list(set(have))
for i in range(len(alf)):
    if not(alf[i] in have):
        print(alf[i])
        exit()
print("None")

Submission status: Accepted

Solution code:
import string

s = set(input())

abc = set(string.ascii_lowercase)
rest = abc - s

if rest:
  print(min(rest))
else:
  print('None')

Submission status: Accepted

Solution code:
S = list(input())
S.sort()
l = list("abcdefghijklmnopqrstuvwxyz")
flag = 0

for i in l:
  if i in S:
    continue
  else:
    print(i)
    flag = 1
    break
    
if flag == 0:
  print("None")

Submission status: Accepted

Solution code:
s=list(input())
a=[chr(i) for i in range(97, 97+26) if chr(i) not in s]
if len(a)==0:print('None')
else:print(a[0])

Submission status: Accepted

Solution code:
alpha=["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"]
s=list(input())
s.sort()
cnt=0
for i in alpha:
    if i not in s:
        print(i)
        cnt+=1
        break
    else:
        continue
if cnt==0:
    print("None")

Submission status: Accepted

Solution code:
alph = [chr(i) for i in range(97, 97+26)]

s = input()
s_li = set(sorted(list(s)))

for v in alph:
    if v not in s_li:
        print(v)
        exit(0)
print('None')

Submission status: Accepted

Solution code:
import string
s = set(input())
alp = sorted(string.ascii_lowercase,reverse=True)
ans = 'None'
for i in alp:
    if not i in s:
        ans = i
print(ans)

Submission status: Accepted

Solution code:
s=input()
l='abcdefghijklmnopqrstuvwxyz'
a=True
for i in range(26):
    if s.count(l[i])==0:
        print(l[i])
        a=False
        break
if a==True:
    print('None')

Submission status: Accepted

Solution code:
S = input()
s = set(S)
base = "abcdefghijklmnopqrstuvwxyz"
Base = set(list(base))
ans = set(Base.difference(s))
if len(s) == 26:
    ans = None
else:
    ans = min(ans)
print(ans)

Submission status: Accepted

Solution code:
s = input()
ans = "None"

for i in range(26):
    test = i + 97
    if chr(test) not in s:
        ans = chr(test)
        break

print(ans)

Submission status: Accepted

Solution code:
s=input()
a=sorted("qwertyuiopasdfghjklzxcvbnm")

b=sorted(list(set(s)))
for x in a:
    if not x in b:
        print(x)
        break
else:
    print("None")

Submission status: Accepted

Solution code:
s = input()
alp = [ 0 for _ in range(27) ]
for ss in s:
    alp[ord(ss)-ord("a")] += 1

for i in range(27):
    if i == 26:
        print("None")
        break
    if alp[i] == 0:
        print(chr(ord("a")+i))
        break

Submission status: Accepted

Solution code:
s = input()

flg = True
for i in "abcdefghijklmnopqrstuvwxyz":
    if i not in s:
        print(i)
        flg = False
        break

if flg:
    print("None")

Submission status: Accepted

Solution code:
s=set(input())
a=[]
for i in s:
  a.append(ord(i)-ord("a"))
for i in range(26):
  if i not in a:
    print(chr(i+ord("a")))
    break
if len(a)==26:
  print("None")

Submission status: Accepted

Solution code:
s = input()
alp = "abcdefghijklmnopqrstuvwxyz"
for i in alp:
	if i not in s:
		print (i)
		exit()
print ("None")

Submission status: Accepted

Solution code:
S=input()
alpha="abcdefghijklmnopqrstuvwxyz"
l=[]
for s in alpha:
    if s not in S:
        l.append(s)
if len(l)==0:
    print("None")
    exit()
l.sort()
print(l[0])

Submission status: Accepted

Solution code:
# import sys
# import math #sqrt
# import decimal
# import queue # queue
# import bisect
# import heapq # priolity-queue
# import time
# import itertools
# import collections # deque
# from operator import itemgetter
# from fractions import Fraction

mod = int(1e9+7)
INF = 1<<29
lINF = 1<<35

def main():
    s = input()
    for i in range(ord('a'),ord('z')+1):
        res = 1
        for j in range(len(s)):
            if s[j]==chr(i):
                res = 0
                break
        if res:
            print(chr(i))
            return 0
    print("None")
    return

if __name__=='__main__':
    main()

Submission status: Accepted

Solution code:
from sys import exit
alphabet = "abcdefghijklmnopqrstuvwxyz"
S = input()
for i in alphabet:
  if i not in S:
    print(i)
    exit()
print("None")

Submission status: Accepted

Solution code:
S = list(set(list(input())))
S.sort(reverse=False)
n = 97

for i in range(len(S)):
  if S[i] != chr(n):
    print(chr(n))
    exit()
  n += 1

if len(S) == 26:
	print('None')
else:
	print(chr(n))

Submission status: Accepted

Solution code:
S = input()
ans='None'
for i in range(26):
  s = chr(ord('a') + i)
  if s not in S:
    ans = s
    break
print(ans)

#print(*ans, sep='\n')

Submission status: Accepted

Solution code:
import sys

S = input()
alfa = [chr(i) for i in range(97, 97+26)]
l = [0] * 26

for i in range(len(S)):
    index = alfa.index(S[i])
    l[index] += 1

for i in range(len(l)):
    if l[i] == 0:
        print(alfa[i])
        sys.exit()
print("None")

Submission status: Accepted

Solution code:
a=set([chr(i) for i in range(97, 97+26)])
s=list(input())
for i in set(s):
    a.remove(i)
if a==set():
    print("None")
else:
    b=sorted(list(a))
    print(b[0])

Submission status: Accepted

Solution code:
s=input()
freq=[0]*26
for i in s:
    freq[ord(i)-ord('a')]=1
if sum(freq)==26:
    print('None')
else:
    for i in range(26):
        if freq[i]==0:
            print(chr(ord('a')+i))
            break

Submission status: Accepted

Solution code:
s = set(list(input()))
b = set(list("abcdefghijklmnopqrstuvwxyz"))

l = sorted(list(b-s))

if l == []:
  print("None")
else:
  print(sorted(list(b-s))[0])

Submission status: Accepted

Solution code:
s = input()

li = [0] * 26

for i in range(len(s)):
    s1 = s[i]
    li[ord(s1) - 97] += 1

for i in range(26):
    if li[i] == 0:
        print(chr(i+97))
        exit()

print('None')

Submission status: Accepted

Solution code:
# Author: cr4zjh0bp
# Created: Sun Mar 22 22:02:37 UTC 2020
import sys
 
stdin = sys.stdin
inf = 1 << 60
mod = 1000000007
 
ni      = lambda: int(ns())
nin     = lambda y: [ni() for _ in range(y)]
na      = lambda: list(map(int, stdin.readline().split()))
nan     = lambda y: [na() for _ in range(y)]
nf      = lambda: float(ns())
nfn     = lambda y: [nf() for _ in range(y)]
nfa     = lambda: list(map(float, stdin.readline().split()))
nfan    = lambda y: [nfa() for _ in range(y)]
ns      = lambda: stdin.readline().rstrip()
nsn     = lambda y: [ns() for _ in range(y)]
ncl     = lambda y: [list(ns()) for _ in range(y)]
nas     = lambda: stdin.readline().split()

from collections import Counter
import string

s = ns()
c = Counter(s)
d = dict(c)

ans = '$'
for i in range(len(string.ascii_lowercase)):
    if d.get(string.ascii_lowercase[i], 0) == 0:
        ans = string.ascii_lowercase[i]
        break
print("None" if ans == "$" else ans)