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:
s=input()
li="abcdefghijklmnopqrstuvwxyz"

for i in range(len(li)):
    if li[i] not in s:
        print(li[i])
        exit()

print("None")

Submission status: Accepted

Solution code:
S = set(input())
alpha = set('abcdefghijklmnopqrstuvwxyz')
if S == alpha:
  print('None')
else:
  ans = sorted(alpha - S)
  print(ans[0])

Submission status: Accepted

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

for str in S:
  if str in ss:
    ss.remove(str)

if len(ss)>0:
  print(sorted(ss)[0])
else:
  print("None")

Submission status: Accepted

Solution code:
S=sorted(set(input()))
ans=None
for i in range(97,97+26):
  if chr(i) not in S:
    ans=chr(i)
    break
print(ans)

Submission status: Accepted

Solution code:
S=input()

#ord('a')文字からアスキーコードを取得
#chr(97)アスキーコードから文字を取得
for i in range(26):
    c = chr(ord('a') + i)
    if S.count(c) == 0:
        print(c)
        exit(0)
print('None')

Submission status: Accepted

Solution code:
a=set(range(26))-set([ord(i)-97for i in input()])
print(chr(min(a)+97)if a else'None')

Submission status: Accepted

Solution code:
a=set(range(26))-set([ord(i)-97for i in input()])
print('abcdefghijklmnopqrstuvwxyz'[min(a)]if a else'None')

Submission status: Accepted

Solution code:
s = input()
for k in range(26):
    c = chr(ord('a') + k)
    if s.count(c) == 0:
        print(c)
        exit(0)
print("None")

Submission status: Accepted

Solution code:
s=input()

s=list(s)
    
alf = [chr(ord('a') + i) for i in range(26)]

for i in alf:
    if i not in s:
        print(i)
        exit()
print('None')

Submission status: Accepted

Solution code:
alp=set(list("abcdefghijklmnopqrstuvwxyz"))
S=alp - set(list(input()))
print("None" if len(S)==0 else min(S))

Submission status: Accepted

Solution code:
s = set(input())
ans = "None"
for i in range(26):
    if chr(97+i) not in s:
        ans = chr(97+i)
        break
print(ans)

Submission status: Accepted

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

Submission status: Accepted

Solution code:
s = input()
a = list("abcdefghijklmnopqrstuvwxyz")
for i in sorted(s):
    if i in a:
        a.remove(i)

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

Submission status: Accepted

Solution code:
import collections

s = input()

col = collections.Counter(s)

for c in "abcdefghijklmnopqrstuvwxyz":
    if c not in col:
        print(c)
        exit()

print("None")

Submission status: Accepted

Solution code:
a = input()
a_l = 'abcdefghijklmnopqrstuvwxyz'
for i in range(26):
  if a.count(a_l[i])>=1:
    continue
  else:
    print(a_l[i])
    exit()
print('None')

Submission status: Accepted

Solution code:
def check(S):
  for i in range(97, 123):
    if chr(i) not in S:
      return chr(i)
  return 'None'


if __name__ == "__main__":
  S = set(input())
  print(check(S))

Submission status: Accepted

Solution code:
s = list(input())
a = [chr(ord('a') + i) for i in range(26)]
cnt = [0]*26
for i in range(len(s)):
    ind = a.index(s[i])
    cnt[ind] += 1
for i in range(len(cnt)):
    if cnt[i] == 0:
        print(a[i])
        exit()
print("None")

Submission status: Accepted

Solution code:
#!/usr/bin/env python3
import sys


def solve(S: str):
    a = {chr(c) for c in range(ord("a"), ord("z") + 1)} - set(S)
    print(sorted(a)[0] if a else "None")


def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    S = next(tokens)  # type: str
    solve(S)


if __name__ == '__main__':
    main()

Submission status: Accepted

Solution code:
s = set(input())
s = list(s)
list =["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"]
l = len(s)
for i in range(l):
  list.remove(s[i])
if list ==[]:
  print('None')
else:
  print(list[0])

Submission status: Accepted

Solution code:
s = input().strip()
chars = list(set(s))
chars.sort()
dic = {"a": 0,
       "b": 1,
       "c": 2,
       "d": 3,
       "e": 4,
       "f": 5,
       "g": 6,
       "h": 7,
       "i": 8,
       "j": 9,
       "k": 10,
       "l": 11,
       "m": 12,
       "n": 13,
       "o": 14,
       "p": 15,
       "q": 16,
       "r": 17,
       "s": 18,
       "t": 19,
       "u": 20,
       "v": 21,
       "w": 22,
       "x": 23,
       "y": 24,
       "z": 25
       }
swap = {v: k for k, v in dic.items()}
ans = "None"
count = 0
for c in chars:
    if dic[c] != count:
        ans = swap[count]
        break
    count += 1
if count <= 25:
    print(swap[count])
else:
    print(ans)

Submission status: Accepted

Solution code:
s=input()
alp=['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']
ss=sorted(s)
for i in alp:
    if i not in ss:
        print(i)
        break
else:
    print('None')

Submission status: Accepted

Solution code:
import sys

s = input()

alphabet = [0]*26

for i in range(len(s)):
    num_alphabet = ord(s[i])
    alphabet[num_alphabet - 97] = 1

index = -1
for i in range(len(alphabet)):
    if alphabet[i] == 0:
        index = i
        break

print("None") if index == -1 else print(chr(index+97))

Submission status: Accepted

Solution code:
s = input()
ans_list = [0] * 26

for i in s:
    i = ord(i) - 97
    ans_list[i] += 1

for i, s in enumerate(ans_list):
    if s==0:
        print(chr(i+97))
        exit()

print('None')

Submission status: Accepted

Solution code:
s = input(); f = 0
words = ['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(words)):
    if words[i] not in s:
        print(words[i])
        f = 1
        break
    
if f == 0:
    print('None')

Submission status: Accepted

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

ans = "None"
for i in range(97, 97+26):
    if not chr(i) in s:
        ans = chr(i)
        break

print(ans)

Submission status: Accepted

Solution code:
alph = ["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())
ans = 100
for i in range(26):
    c = 0
    for j in s:
        if alph[i] == j:
            c = 1
            break
    if c == 0:
        ans = i
        break
if ans == 100:
    print("None")
else:
    print(alph[ans])

Submission status: Accepted

Solution code:
import string

S = input()

flag = False
for l in string.ascii_lowercase:
    if l not in S:
        output = l
        flag = True
        break

if flag:
    print(output)
else :
    print('None')

Submission status: Accepted

Solution code:
S = list(set(input()))
S.sort()
for i in range(0x61,0x7b):
    if chr(i) not in S:
        print(chr(i))
        exit()
print('None')

Submission status: Accepted

Solution code:
str = input()
abc = ['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','aa']
i = 0
while abc[i] in str:
    if i < 26:
        i += 1
    else:
        break

if i < 26:
    print(abc[i])

else:
    print("None")

Submission status: Accepted

Solution code:
S = list(input())
C = ['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.sort()
set(S)
for c in C:
    if c in(S):
        if c == "z":
            print('None')
        continue
    else:
        print(c)
        break

Submission status: Accepted

Solution code:
s = list(input())
# s.sort()
ans = 'None'
t = []
for i in range(len(s)):
  t.append(ord(s[i]))
for i in range(97, 123):
  if not i in t:
    ans = chr(i)
    break
print(ans)

Submission status: Accepted

Solution code:
s=sorted(set(input()))
test="abcdefghijklmnopqrstuvwxyz"
for i in range(len(test)):
    if (s[i]!=test[i]):
        print(test[i])
        break
    if (s[i]==test[i] and i==len(s)-1 and i!=len(test)-1):
        print(test[i+1])
        break
else:
    print("None")

Submission status: Accepted

Solution code:
S=input()
N=len(S)

T=[0]*26
ans=0

for i in range(N):
    T[ord(S[i])-97]+=1

for j in range(26):
    if T[j]==0:
        ans=chr(j+97)
        break

print("None" if ans==0 else ans)

Submission status: Accepted

Solution code:
# import bisect
# import copy
# import fractions
# import math
# import numpy as np
# from collections import Counter, deque
# from itertools import accumulate,permutations, combinations,combinations_with_replacement,product

def resolve():
    s=list(input())

# アルファベット小文字→(97, 123)を入力に入れる
# アルファベット大文字→(65, 91)
# 半角数字→(48, 58)
# ひらがな→(12353, 12436)
# カタカナ→(12449, 12532+1)
# 全角数字→(65296, 65306)



    def moji_list(*args):
        moji = []
        for i in range(len(args)):
            moji.extend([chr(j) for j in range(args[i][0], args[i][1])])
        return moji

    lowercase = moji_list((97,123))

    print(min(set(lowercase)-set(s) or ['None']))

resolve()

Submission status: Accepted

Solution code:
# import bisect
# import copy
# import fractions
# import math
# import numpy as np
# from collections import Counter, deque
# from itertools import accumulate,permutations, combinations,combinations_with_replacement,product

def resolve():
    s=list(input())

    # アルファベット小文字→(97, 123)
    # アルファベット大文字→(65, 91)
    # 半角数字→(48, 58)
    # ひらがな→(12353, 12436)
    # カタカナ→(12449, 12532+1)
    # 全角数字→(65296, 65306)

    def moji_list(*args):
        moji = []
        for i in range(len(args)):
            moji.extend([chr(j) for j in range(args[i][0], args[i][1])])
        return moji

    lowercase = moji_list((97,123))

    for i in s:
        if i in lowercase:
            lowercase.remove(i)
    print(lowercase[0] if len(lowercase)!=0 else 'None')

resolve()

Submission status: Accepted

Solution code:
# import bisect
# import copy
# import fractions
# import math
# import numpy as np
# from collections import Counter, deque
# from itertools import accumulate,permutations, combinations,combinations_with_replacement,product

def resolve():
    s=list(input())
    lowercase = list('abcdefghijklmnopqrstuvwxyz')

    for i in s:
        if i in lowercase:
            lowercase.remove(i)
    print(lowercase[0] if len(lowercase)!=0 else 'None')

resolve()

Submission status: Accepted

Solution code:
s = input()
li = []
alf = ["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 x in alf:
    if x not in s:
        li.append(x)
if li == []:
    print("None")
else:
    print(min(li))

Submission status: Accepted

Solution code:
S=input()
words=[a for a in S]
arufa=[chr(i) for i in range(97,123)]
for word in words:
    if word in arufa:
        arufa.remove(word)
if arufa==[]:
    print('None')
else:
    print(arufa[0])

Submission status: Accepted

Solution code:
s = sorted(list(set(input())))
alpha = list('abcdefghijklmnopqrstuvwxyz')
for i in alpha:
    if i not in s:
        print(i)
        break
else:
    print('None')

Submission status: Accepted

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

Submission status: Accepted

Solution code:
flag=1
a=input()
for i in 'abcdefghijklmnopqrstuvwxyz':
  if i not in a:flag=0;break
print('None'if flag else i)

Submission status: Accepted

Solution code:
import sys

d={}
ss=input().strip()
for s in ss:
  d[s]=1

for i in range(ord("a"), ord("z")+1):
  if chr(i) not in d:
    print(chr(i))
    sys.exit()
print("None")

Submission status: Accepted

Solution code:
import sys

a=ord("a")
z=ord("z")

d={}
ss=input().strip()
for s in ss:
  d[s]=1

for i in range(ord("a"), ord("z")+1):
  if chr(i) not in d:
    print(chr(i))
    sys.exit()
print("None")

Submission status: Accepted

Solution code:
print(min(set(map(chr,range(97,123)))-set(input())or[None]))

Submission status: Accepted

Solution code:
s = input()
base = "abcdefghijklmnopqrstuvwxyz"
L = [i for i in base]
L = set(L)

s = set(s)
ans = list(L-s)

try:
    print(sorted(ans)[0])
except:
    print("None")

Submission status: Accepted

Solution code:
s = set(list(str(input())))
s1=list(sorted(s))
for i in range(len(s1)+1):
    if not chr(i+97) in s1:
        print(chr(i+97))
        break
    elif chr(i+97)=='z':
        print(None)
        break

Submission status: Accepted

Solution code:
alp=['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_ = list(set(s))
#print(s)
#print(s_)
s.sort()
s_.sort()
#print(s)
#print(s_)
        
l=[]
cnt=0
for i in range(len(alp)):
            if s.count(alp[i]):
                        pass
            else:
                        l.append(alp[i])
                        cnt+=1
#print(l)
if cnt==0:
            print('None')
else:
            print(min(l))
exit()

Submission status: Accepted

Solution code:
strings = str(input())
string_list = list(strings)
string_set = set(string_list)

import string

alpha = list(string.ascii_lowercase)
alpha_set = set(alpha)

ans = (alpha_set - string_set)
ans = list(ans)
ans.sort()

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

Submission status: Accepted

Solution code:
def main():
    import sys
    #input = sys.stdin.readline
    sys.setrecursionlimit(10000000)
    from collections import Counter, deque
    #from collections import defaultdict
    from itertools import combinations, permutations
    #from itertools import accumulate, product
    from bisect import bisect_left,bisect_right
    from math import floor, ceil
    #from operator import itemgetter

    #mod = 1000000007

    al = 'abcdefghijklmnopqrstuvwxyz' #26
    s = input()
    for i in al:
        if not i in s:
            print(i)
            exit()
    print('None')


if __name__ == '__main__':
    main()

Submission status: Accepted

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

Submission status: Accepted

Solution code:
abc=set([chr(ord('a')+i) for i in range(26)])
S=set(input())
ans=sorted(list(abc.difference(S)))

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

Submission status: Accepted

Solution code:
s = sorted(set(list(str(input()))))
t = list('abcdefghijklmnopqrstuvwxyz')
ans = ''
for i in range(26):
    if t[i] not in s:
        ans = t[i]
        break
else:
    ans = 'None'
print(ans)

Submission status: Accepted

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

Submission status: Accepted

Solution code:
s = input()
b = [0]*26
for c in s:
  b[ord(c)-ord("a")]+=1
for i,c in enumerate(b):
  if c == 0:
    print(chr(i+ord("a")))
    exit()
print("None")

Submission status: Accepted

Solution code:
# -*- coding: utf-8 -*-
s = list(str(input()))

alph = ['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']
"""
if len(set(s)) >= 26:
    print("None")
    exit()
for i in alph:
    for j in s:
        if not(i in s):
            print(i)
            exit()
"""

check = [False] * 26
for i in s:
    for j in range(26):
        if i == alph[j]:
            check[j] = True
tmp = 0
for i in range(26):
    if check[i] == False:
        print(alph[i])
        exit()
    if check[i]:
        tmp += 1
if tmp == 26:
    print("None")

Submission status: Accepted

Solution code:
# -*- coding: utf-8 -*-
s = list(str(input()))

alph = ['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']
if len(set(s)) >= 26:
    print("None")
    exit()
for i in alph:
    for j in s:
        if not(i in s):
            print(i)
            exit()

Submission status: Accepted

Solution code:
S=input()
cnt=[0]*26
for i in S:
    cnt[ord(i)-97]+=1
for i in range(26):
    if(cnt[i]==0):
        print(chr(i+97))
        exit()
print("None")

Submission status: Accepted

Solution code:
s = sorted(input())
alphabet = 'abcdefghijklmnopqrstuvwxyz'
for i in range(26):
    if not alphabet[i] in s:
        print(alphabet[i])
        break
    if alphabet[i] == 'z':
        print("None")

Submission status: Accepted

Solution code:
S = input()

S = sorted(S)

S_dict = {}
cnt = 0
#ord : return number of character based on character
#chr : return character based on number of character
for i in range(ord("a"), ord("z") +1):
  S_dict[i] = S.count(chr(i))

#print(S_dict)

ans =None
for i in range(ord("a"), ord("z") +1):
  if S_dict[i] == 0:
    ans = chr(i)
    break
    
print(ans)

Submission status: Accepted

Solution code:
import sys
input = sys.stdin.readline
import string

S = input().rstrip('\r')
alph = string.ascii_lowercase
S_map = {}
for c in alph:
    S_map[c] = False
for s in S:
    S_map[s] = True
ans = 'None'
for c in alph:
    if not S_map[c]:
        ans = c
        break
print(ans)

Submission status: Accepted

Solution code:
import sys
input = sys.stdin.readline

def I(): return int(input())
def MI(): return map(int, input().split())
def LI(): return list(map(int, input().split()))

def main():
    mod=10**9+7
    S=set(list(input()))
    T=[]
    for i in range(26):
        T.append(chr(i+97))
    T=set(T)
    ans=list(T-S)

    if ans==[]:
        print("None")
    else:
        ans.sort()
        print(ans[0])
    
    
    

main()

Submission status: Accepted

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

for i in "abcdefghijklmnopqrstuvwxyz":
    if i not in s:
        ans = i
        break
        
print(ans)

Submission status: Accepted

Solution code:
#ABC071

s = sorted(set(input()))
l = "abcdefghijklmnopqrstuvwxyz"
for i in l:
    
    if i not in s:
        print(i)
        break
        
else:
    print("None")
    
    
## if i in s == False はうまくいかない
##in/not inを使う

Submission status: Accepted

Solution code:
al = list("abcdefghijklmnopqrstuvwxyz")
s = list(input())
ans = "None"
for i in al:
  if not i in s:
    ans = i
    break
print(ans)

Submission status: Accepted

Solution code:
S=input()
alpha=set([i for i in "abcdefghijklmnopqrstuvwxyz"])
ans=alpha-set(list(S))
ans=sorted(ans)
print(ans[0] if len(ans)>0 else 'None')

Submission status: Accepted

Solution code:
#!/usr/bin/env python3
from collections import defaultdict,deque
from heapq import heappush, heappop
from bisect import bisect_left, bisect_right
import sys, random, itertools, math
sys.setrecursionlimit(10**5)
input = sys.stdin.readline
sqrt = math.sqrt
def LI(): return list(map(int, input().split()))
def LF(): return list(map(float, input().split()))
def LI_(): return list(map(lambda x: int(x)-1, input().split()))
def II(): return int(input())
def IF(): return float(input())
def LS(): return list(map(list, input().split()))
def S(): return list(input().rstrip())
def IR(n): return [II() for _ in range(n)]
def LIR(n): return [LI() for _ in range(n)]
def FR(n): return [IF() for _ in range(n)]
def LFR(n): return [LI() for _ in range(n)]
def LIR_(n): return [LI_() for _ in range(n)]
def SR(n): return [S() for _ in range(n)]
def LSR(n): return [LS() for _ in range(n)]
mod = 1000000007
inf = float('INF')

#solve
def solve():
    s = list(set(S()))
    lis = [chr(i) for i in range(ord("a"), ord("z") + 1)]
    for si in s:
        if si in lis:
            lis.remove(si)
        # print(si,lis)
    lis.sort()
    if lis == []:
        print("None")
    else:
        print(lis[0])
    return


#main
if __name__ == '__main__':
    solve()

Submission status: Accepted

Solution code:
import numpy as np

s = input()
t = list("abcdefghijklmnopqrstuvwxyz")
s = list(sorted(set(s)))

ans = "None"
for c in t:
    if c not in s:
        ans = c
        break
print(ans)

Submission status: Accepted

Solution code:
import numpy as np

s = input()
t = list("abcdefghijklmnopqrstuvwxyz")
s = list(sorted(set(s)))

ans = "None"
ls = len(s)
for i in range(ls):
    if s[i] != t[i]:
        ans = t[i]
        break
    elif s[i] == t[i] and i == ls-1 and i < 25:
        ans = t[i+1]
        break
        
print(ans)

Submission status: Accepted

Solution code:
s = input()
n = len(s)
alp = [False] * 26
for i in range(n):
    num = ord(s[i]) - ord('a')
    alp[num] = True
ok = 0
for i in range(26):
    if alp[i]:
        continue
    print(chr(ord('a') + i))
    ok = 1
    break
if ok == 0:
    print("None")

Submission status: Accepted

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

Submission status: Accepted

Solution code:
#071_B
s=input()
c='a'
while c<='z':
    if c not in s:
        print(c)
        exit()
    c=chr(ord(c)+1)
    
print('None')

Submission status: Accepted

Solution code:
s = input()
ss = sorted(set(s))
cnt = ord('a')
for c in ss:
    if ord(c) == cnt:
        cnt += 1
    else:
        print(chr(cnt))
        exit()
if cnt == ord('{'):
    print('None')
else:
    print(chr(cnt))

Submission status: Accepted

Solution code:
# coding: utf-8

alpha = [chr(ord("a") + i) for i in range(26)]
s = input().rstrip()

tmp = [i for i in alpha if i not in s]

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

Submission status: Accepted

Solution code:
# coding: utf-8
S = input()
alp = "abcdefghijklmnopqrstuvwxyz"
for a in alp:
    if a not in S:
        print(a)
        exit()
print("None")

Submission status: Accepted

Solution code:
# coding: utf-8
alp=["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=input()
lS=list(S)
flg=False

for i in range(len(alp)):
    if alp[i] in lS:
        continue
    else:
        print(alp[i])
        flg=True
        break

if not(flg):
    print("None")

Submission status: Accepted

Solution code:
# coding: utf-8
# Your code here!
al=[chr(ord('a') + i) for i in range(26)]
s = list(input())

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

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

Submission status: Accepted

Solution code:
letters="abcdefghijklmnopqrstuvwxyz"
ans=sorted(set(letters)^set(input()))
print("None" if len(ans)==0 else ans[0])

Submission status: Accepted

Solution code:
l = list()
for i in range(97, 123):
    l.append(chr(i))
s = list(set(input()))
for i in s:
    l.remove(i)
if l == []:
    print("None")
else:
    print(l[0])

Submission status: Accepted

Solution code:
s=sorted(list(set(input())))
al='abcdefghijklmnopqrstuvwxyz'
for i in range(len(s)):
  if s[i]!=al[i]:
    print(al[i])
    exit()
ans=al[len(s)] if len(s)<26 else 'None'
print(ans)

Submission status: Accepted

Solution code:
alphabet_list = [chr(ord('a')+i) for i in range(26)]
alphabet_string = ''.join(alphabet_list)
s = input()
for i in s:
    alphabet_string = alphabet_string.replace(i, '')
if len(alphabet_string) != 0:
    print(alphabet_string[0])
else:
    print('None')

Submission status: Accepted

Solution code:
import string

l = list(input())
l.sort()
d = list(string.ascii_lowercase)

if len(set(l)) == 26:
    print('None')
else:
    for i in range(26):
        if d[i] not in l:
            print(d[i])
            break

Submission status: Accepted

Solution code:
s=input()
alphabet=set([i for i in "abcdefghijklmnopqrstuvwxyz"])
ans=alphabet-set(list(s))
print(sorted(ans)[0]) if len(ans)>0 else print("None")

Submission status: Accepted

Solution code:
alphabet = 'abcdefghijklmnopqrstuvwxyz'
alphabet_list = list(map(str, alphabet))
s = list(input())
s_set = list(set(s))
for s in s_set:
    if s in alphabet_list:
        alphabet_list.remove(s)
if len(alphabet_list) != 0:
    print(alphabet_list[0])
else:
    print('None')

Submission status: Accepted

Solution code:
s = input()
l = [False] * 26
for c in s:
  l[ord(c) - ord('a')] = True
for i in range(26):
  if not l[i]:
    print(chr(97+i))
    exit()
print('None')

Submission status: Accepted

Solution code:
S = input()
alphabet = set([chr(i) for i in range(97, 97+26)])
ans = alphabet - set(list(S))
print(sorted(ans)[0]) if len(ans) > 0 else print('None')

Submission status: Accepted

Solution code:
s = sorted(list(set(list(input()))))
i = 0
while i < len(s) and chr(i+97)==s[i]:
    i += 1
if i<=25:
    print(chr(i+97))
else:
    print("None")

Submission status: Accepted

Solution code:
S = str(input())
ans = 'None'
alfabet = 'abcdefghijklmnopqrstuvwxyz'
for i in alfabet:
    if i not in S:
        ans = i
        break
print(ans)

Submission status: Accepted

Solution code:
N = str(input())
ans = None
for l in "abcdefghijklmnopqrstuvwxyz":
    if l not in N:
        ans = l
        break
print(ans)

Submission status: Accepted

Solution code:
txt = input()
check_list = [0] * 26
base = ord('a')

for c in list(txt):
    check_list[ord(c) - base] = 1
    
ans = -1    
for i in range(26):
    if check_list[i] == 0:
        ans = base + i
        break
    
if ans == -1:
    print('None')
else:
    print(chr(ans))

Submission status: Accepted

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

for i in s:
    a.remove(i)

if a:
    print(a[0])
else:
    print("None")

Submission status: Accepted

Solution code:
S = str(input())

reference = 'abcdefghijklmnopqrstuvwxyz'

for i in range(26):
    if reference[i] not in S:
        print(reference[i])
        break
    elif i == 25:
        print('None')

Submission status: Accepted

Solution code:
from string import ascii_lowercase


def main():
    string = input()
    count = {}
    for lcase in ascii_lowercase:
        count[lcase] = 0
    for s in string:
        count[s] += 1
    count = sorted(count.items(), key=lambda x: x[0])
    for i, count in enumerate(count):
        if count[1] == 0:
            print(ascii_lowercase[i])
            break
    else:
        print("None")


if __name__ == '__main__':
    main()

Submission status: Accepted

Solution code:
alphabet='abcdefghijklmnopqrstuvwxyz'
S=input()
ans="None"
for a in alphabet:
    if S.count(a)==0:
        ans=a
        break
print(ans)

Submission status: Accepted

Solution code:
S = input()

x = "abcdefghijklmnopqrstuvwxyz"
ans = "None"
for i in x:
  if i in S:
    pass
  else:
    ans = i
    break

print(ans)

Submission status: Accepted

Solution code:
def cal_word(n):
	return n - 97

def cal_word_rev(n):
	return n + 97

S = list(map(str,input()))
S_new = sorted(S)
index = -1
S_ans = []

for i in range(0, 26):
	S_ans.append('false')

for i in range(0, len(S)):
	S_ans[cal_word(ord(S[i]))] = 'true'

for i in range(0, 26):
	if S_ans[i] == 'false':
		index = i
		break
if index == -1:
	print('None')
else:
	print(chr(cal_word_rev(index)))

Submission status: Accepted

Solution code:
S = input()
eng_list = [i for i in range(97, 123)]
for i in range(len(S)):
    for j in range(len(eng_list)):
        if ord(S[i]) == eng_list[j]:
            eng_list.pop(j)
            break
print(chr(eng_list[0])) if len(eng_list) != 0 else print("None")

Submission status: Accepted

Solution code:
s = input()
x = "abcdefghijklmnopqrstuvwxyz"
ans = "None"
for i in x:
    if i in s:
        pass
    else:
        ans = i
        break
print(ans)

Submission status: Accepted

Solution code:
from string import ascii_lowercase as ascii


def main(s):
    _s = set(s)

    for a in ascii:
        if not a in s:
            print(a)
            return

    print('None')


if __name__ == "__main__":
    s = input()

    main(s)

Submission status: Accepted

Solution code:
A=input()
B=sorted(set(A))

def aaa(a):
  return(ord(a))

C=list(map(aaa,B))

for i in range(26):
  if (i+97 in C)!=1:
    print(chr(i+97))
    break
  if i==25:
    print("None")

Submission status: Accepted

Solution code:
s = input()
for i in range(97, 123):
    if chr(i) not in s:
        print(chr(i))
        exit(0)
print('None')

Submission status: Accepted

Solution code:
S = input()
alpha_li = [chr(i) for i in range(97, 97 + 26)]
for s in S :
    if s in alpha_li :
        alpha_li.remove(s)
if alpha_li == [] :
    print("None")
else :
    print(alpha_li[0])

Submission status: Accepted

Solution code:
S = input()

set_alphabet = {chr(i) for i in range(97,123)}

list_ans = list(set_alphabet - set(S))
list_ans.sort()

if list_ans :
    print(list_ans[0])
else :
    print("None")

Submission status: Accepted

Solution code:
s=input()
ans="None"
for i in range(97, 97+26):
    if chr(i) not in s:
        ans=chr(i)
        break
print(ans)

Submission status: Accepted

Solution code:
s = list(input())

A = [chr(i) for i in range(ord("a"), ord("z") + 1)]
t = 0
for i in A:
    if i not in s:
        t += 1
        print(i)
        break
if t == 0:
    print("None")

Submission status: Accepted

Solution code:
S = input()
atoz = [chr(i) for i in range(ord('a'), ord('z') + 1)]
ans = ''

for s in sorted(atoz, reverse=True):
  if s not in S:
    ans = s

if ans == '':
  print('None')
else:
  print(ans)

Submission status: Accepted

Solution code:
# -*- coding: utf-8 -*-


#----------
S = input().strip()
#----------
all_alphabet=[chr(ord('a') + i) for i in range(26)]

check_alphabet=all_alphabet
for word in S:
    if word in check_alphabet:
        check_alphabet.remove(word)

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

Submission status: Accepted

Solution code:
diff = set('abcdefghijklmnopqrstuvwxyz') - set(input())
if diff:
    print(sorted(diff)[0])
else:
    print('None')

Submission status: Accepted

Solution code:
S="abcdefghijklmnopqrstuvwxyz"
T=list(input())
for i in range(26):
  x=S[i]
  if not(x in T):
    print(x)
    break
else:
  print('None')

Submission status: Accepted

Solution code:
s=str(input())

for i in range(26):
    if s.count(chr(97+i))==0:
        print(chr(97+i))
        break
else:
    print("None")

Submission status: Accepted

Solution code:
r = list(set(range(97, 123)) - set(map(ord, list(input()))))
if r:
    print(chr(min(r)))
else:
    print('None')

Submission status: Accepted

Solution code:
S = input()
A = list("abcdefghijklmnopqrstuvwxyz")
flag = [a for a in A if a not in S]

if flag:
    flag.sort()
    print(flag[0])
else:
    print("None")

Submission status: Accepted

Solution code:
def main():
    S = set(input())
    ans = "None"
    for i in range(97, 97+26):
        if chr(i) not in S:
            ans = chr(i)
            break
    print(ans)

if __name__ == '__main__':
    main()

Submission status: Accepted

Solution code:
s=list(input())
a=list("abcdefghijklmnopqrstuvwxyz")
a=[i for i in a if i not in s]
if a:
    a.sort()
    print(a[0])
else:
    print("None")