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:
#!/usr/bin/env python3
# -*- coding: utf-8 -*-
s=input()
r='None'
for i in range(ord('a'),ord('z')+1):
  if s.count(chr(i))==0:
    r=chr(i)
    break
print(r)

Submission status: Accepted

Solution code:
import string

S = str(input())
ans = []

for a in string.ascii_lowercase:
    isExist = False
    for i in range(len(S)):
        if S[i] == a:
            isExist = True
    if isExist == False:
        ans.append(a)

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

Submission status: Accepted

Solution code:
s=list(input())
res="None"
s.sort()
str="abcdefghijklmnopqrstuvwxyz"

for i in range (26):
    if not(str[i] in s):
        res=str[i]
        break
 
print(res)

Submission status: Accepted

Solution code:
from sys import stdin


def main() -> None:
    s = next_str()
    print(judge(s))


def judge(s: str) -> str:
    for i in range(ord('a'), ord('z') + 1):
        c = chr(i)
        if c not in s:
            return c
    return "None"


def next_str() -> str:
    result = ""
    while True:
        tmp = stdin.read(1)
        if tmp.strip() != "":
            result += tmp
        elif tmp != '\r':
            break
    return result


if __name__ == '__main__':
    main()

Submission status: Accepted

Solution code:
s = input()
al = ["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(26):
  if s.count(al[i]) == 0:
    print(al[i])
    break
  elif i == 25:
    print("None")

Submission status: Accepted

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

Submission status: Accepted

Solution code:
S = set(input())

for c in list("abcdefghijklmnopqrstuvwxyz"):
    if c not in S:
        print(c)
        break
else:
    print("None")

Submission status: Accepted

Solution code:
n = set("abcdefghijklmnopqrstuvwxyz")
a = sorted(list(n - set(input())))
if len(a) == 0:
    print("None")
else:
    print(a[0])

Submission status: Accepted

Solution code:
A=str(input())
P=[]
for i in range(26):
    p=chr(ord("a")+i)
    P.append(p)

ANS=[]
for i in P:
    if i not in A:
        ANS.append(i)
if len(ANS)==0:
    print("None")
else:
    print(ANS[0])

Submission status: Accepted

Solution code:
s = raw_input()
#print(s)

ch_lst = "abcdefghijklmnopqrstqvwxyz"
#ch_lst = [chr(i) for i in range(ord('a'), ord('z')+1)]
#print(ch_lst)

match = 0
for j in ch_lst:
  ch = s.find(j)
  if ch != -1:
    continue
  else:
    match = 1
    break

if match == 0:
  print("None")
elif match == 1:
  print(j)

Submission status: Accepted

Solution code:
S = input()
X = "abcdefghijklmnopqrstuvwxyz"
S_index = sorted(set(S), reverse = True)
S_list = list(S_index)
X_list = list(sorted(X, reverse = True))
answer = None
for i in X_list:
  for n in S_list:
    if i == n:
      break
    elif n == S_list[-1]:
      answer = i
print(answer)

Submission status: Accepted

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

for _ in a:
  if _ in s:
    pass
  else:
    ans = _
    break
    
print(ans)

Submission status: Accepted

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

Submission status: Accepted

Solution code:
alpha = [chr(i) for i in range(97, 97+26)]
S = input()
a = sorted(set(alpha) - set(S))

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

Submission status: Accepted

Solution code:
S = list(input())
moji = [chr(i) for i in range(97, 97+26)]
for alp in moji:
    if alp not in S:
        print(alp)
        break
else:
    print('None')

Submission status: Accepted

Solution code:
import sys

s = input()

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

Submission status: Accepted

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

if s==a:
    print('None')
else:
    b=sorted(list(a-s))
    print(str(b[0]))

Submission status: Accepted

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

Submission status: Accepted

Solution code:
S=input()
ans='None'
arr=[0 for _ in range(26)]
for x in S:
    arr[ord(x)-ord('a')]=1

for i,x in enumerate(arr):
    if x == 0:
        ans=chr(ord('a')+i)
        break
print(ans)

Submission status: Accepted

Solution code:
def main():
	s = input()

	start = ord('a')
	end = ord('z')

	for i in range(start,end+1):
		#print("*", chr(i))
		flg = 0
		for c in s:
			if c == chr(i):
				flg = 1
				break
		if flg == 0:
			print(chr(i))
			return
	print("None")
	return

if __name__ == '__main__':
	main()

Submission status: Accepted

Solution code:
S=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"]
B=[c for c in S]
C=list(set(A)^set(B))
A=sorted(set(C),key=A.index)
if len(A)==0:
    print("None")
else:
    print(A[0])

Submission status: Accepted

Solution code:
def conversion(a):
    num = ord(a) - 97
    return num
c = [] #バケット法用
b = [] #数字に変換したリスト
a = list(input())
ans = 0
#文字列を数字に変換
for i in a:
    b.append(conversion(i))


#バケット法
for i in range(26):
    c.append(0)
for i in b:
    c[i] = 1

#存在しない数字を探す
for i in c:
    if i == 0:
        break
    else:
        ans += 1

#答えをアルファベットに変換

if ans == 26:
    print("None")
else:
    print(chr(ans + 97))

Submission status: Accepted

Solution code:
import sys
stdin = sys.stdin

def li(): return map(int, stdin.readline().split())
def li_(): return map(lambda x: int(x)-1, stdin.readline().split())
def lf(): return map(float, stdin.readline().split())
def ls(): return stdin.readline().split()
def ns(): return stdin.readline().rstrip()
def lc(): return list(ns())
def ni(): return int(stdin.readline())
def nf(): return float(stdin.readline())

s = lc()

alpha = [chr(i) for i in range(ord("a"), ord("z")+1)]
lst = [0]*26

for i,a in enumerate(alpha):
    lst[i] = s.count(a)
    
exist = False
for i in range(26):
    if lst[i] == 0:
        print(alpha[i])
        exist = True
        break
        
if not exist:
    print("None")

Submission status: Accepted

Solution code:
S = input()
for i in range(26):
    c = chr(i + ord('a'))
    if c not in S:
        print(c)
        exit()
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 = set(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:
listA= list(input())
alphaL = [chr(i) for i in range(97, 97+26)]

index=0
while index < len(listA):
    if listA[index] in alphaL:
        alphaL.remove(listA[index])
    index+=1

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

Submission status: Accepted

Solution code:
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'.split()
s = sorted(list(set(input())))
N = len(s)
i = 0
while(alphabets[i] in s):
    i += 1
    if(i == 26):
        break
if(i == 26):
    print('None')
else:
    print(chr(i+97))

Submission status: Accepted

Solution code:
S = set(input())
abc = "abcdefghijklmnopqrstuvwxyz"
if len(S) == len(abc):
  print(None)
for w in abc:
  if not w in S:
    print(w)
    break

Submission status: Accepted

Solution code:
s = input()

a = [c for c in "abcdefghijklmnopqrstuvwxyz"]


for i in range(len(a)):
    if a[i] not in s:
        print(a[i])
        exit(0)

print("None")

Submission status: Accepted

Solution code:
s=input()
res="None"
for i in range(97,97+26):
    if s.count(chr(i)) == 0:
        res=chr(i)
        break
print(res)

Submission status: Accepted

Solution code:
s = input()
sset = set(s)
ans = 'None'
abc = 'abcdefghijklmnopqrstuvwxyz'
for c in abc:
  if c not in sset:
    ans = c
    break
print(ans)

Submission status: Accepted

Solution code:
s = input()
char_list = list(s)
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 al in alphabets:
    if al not in char_list:
        print(al)
        exit()
print("None")

Submission status: Accepted

Solution code:
S=set(input())
X={'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'}
A=list(X-S)
A.sort()
if A==[]:
  print('None')
else:
  print(A[0])

Submission status: Accepted

Solution code:
Alphabet = []
Alphabet.append("a")
Alphabet.append("b")
Alphabet.append("c")
Alphabet.append("d")
Alphabet.append("e")
Alphabet.append("f")
Alphabet.append("g")
Alphabet.append("h")
Alphabet.append("i")
Alphabet.append("j")
Alphabet.append("k")
Alphabet.append("l")
Alphabet.append("m")
Alphabet.append("n")
Alphabet.append("o")
Alphabet.append("p")
Alphabet.append("q")
Alphabet.append("r")
Alphabet.append("s")
Alphabet.append("t")
Alphabet.append("u")
Alphabet.append("v")
Alphabet.append("w")
Alphabet.append("x")
Alphabet.append("y")
Alphabet.append("z")
S = list(input())
S = list(set(S))
for i in range(len(S)) :
    for j in range(len(Alphabet)) :
        if S[i] == Alphabet[j] :
            Alphabet[j] = "-1"
if Alphabet.count("-1") == len(Alphabet) :
    print("None")
else :
    for k in range(len(Alphabet)) :
        if Alphabet[k] != "-1" :
            print(Alphabet[k])
            break

Submission status: Accepted

Solution code:
a=list(input())
b=[chr(i) for i in range(97, 97+26)]
for x in b:
  if not x in a:
     print(x)
     break
if len(set(a))==26:print('None')

Submission status: Accepted

Solution code:
S = input()
abc = 'abcdefghijklmnopqrstuvwxyz'
dic = {}
for s in abc:
    dic[s] = 0
for s in S:
    dic[s] += 1

for s in abc:
    if dic[s] == 0:
        print(s)
        exit()
print('None')

Submission status: Accepted

Solution code:
a = list(input())
aa = list(set(a))
alpha = [chr(i) for i in range(97,97+26)]


if len(aa) == 26:
    print('None')
else:
    for i in range(26):
        if alpha[i] not in a:
            print(alpha[i])
            break

Submission status: Accepted

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

Submission status: Accepted

Solution code:
S = input()
A = list('abcdefghijklmnopqrstuvwxyz')
flag = True
for i in A:
  if (i not in S):
    flag = False
    break
if flag:
  print('None')
else:
  print(i)

Submission status: Accepted

Solution code:
S = input()
alphabets = set(list('abcdefghijklmnopqrstuvwxyz'))
 
for s in S:
    alphabets.discard(s)
 
if len(alphabets) != 0:
    print(sorted(alphabets)[0])
else:
    print('None')

Submission status: Accepted

Solution code:
S = input()
X = [i for i in "abcdefghijklmnopqrstuvwxyz"]

S = [s for s in S]
S.sort()

for x in X:
    if x not in S:
        print(x)
        exit()

print("None")

Submission status: Accepted

Solution code:
S = input()
alphabets = set(list('abcdefghijklmnopqrstuvwxyz'))

for s in S:
    alphabets.discard(s)

if len(alphabets) != 0:
    print(sorted(alphabets)[0])
else:
    print('None')

Submission status: Accepted

Solution code:
from collections import defaultdict, Counter
from itertools import product, groupby, count, permutations, combinations
from math import pi, sqrt
from collections import deque
from bisect import bisect, bisect_left, bisect_right
from string import ascii_lowercase
from functools import lru_cache
import sys
sys.setrecursionlimit(10000)
INF = float("inf")
YES, Yes, yes, NO, No, no = "YES", "Yes", "yes", "NO", "No", "no"
dy4, dx4 = [0, 1, 0, -1], [1, 0, -1, 0]
dy8, dx8 = [0, -1, 0, 1, 1, -1, -1, 1], [1, 0, -1, 0, 1, 1, -1, -1]

def inside(y, x, H, W):
    return 0 <= y < H and 0 <= x < W


def ceil(a, b):
    return (a + b - 1) // b


def main():
    S = input()
    for c in ascii_lowercase:
        if c not in S:
            print(c)
            return
    print("None")


if __name__ == '__main__':
    main()

Submission status: Accepted

Solution code:
from collections import Counter
S=list(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']
for i in abc:
    if i not in S:
        print(i)
        exit()
print("None")

Submission status: Accepted

Solution code:
s = input()

num = {}
for ss in s:
    num[ss] = 1

ans = 'None'
for i in range(97, 97+26):
    if not chr(i) in num.keys():
        ans = chr(i)
        break
print(ans)

Submission status: Accepted

Solution code:
S = input()

dic = set()

for ch in S:
  dic.add(ch)

if len(dic) == 26:
  print("None")
  exit(0)

for ch in "abcdefghijklmnopqrstuvwxyz":
  if not ch in dic:
    print(ch)
    exit(0)

Submission status: Accepted

Solution code:
a = set("abcdefghijklmnopqrstuvwxyz") - set(input())
if a == set():
    print("None")
else:
    print(min(a))

Submission status: Accepted

Solution code:
import string
a = set(string.ascii_lowercase) - set(input())
if a == set():
    print("None")
else:
    print(min(a))

Submission status: Accepted

Solution code:
import string

s = input()
all = string.ascii_lowercase
rest = list(set(all) - set(s))
if rest == []:
    print('None')
else:
    rest.sort()
    print(rest[0])

Submission status: Accepted

Solution code:
s = set(input())
alphabet = set("abcdefghijklmnopqrstuvwxyz")
print("None" if len(s) == 26 else sorted(alphabet - s)[0])

Submission status: Accepted

Solution code:
s=input()
a='None'
for c in 'abcdefghijklmnopqrstuvwxyz':
    f=0
    for t in s:f|=c==t
    if not f:a=c;break
print(a)

Submission status: Accepted

Solution code:
S = input()
alphbet = 'abcdefghijklmnopqrstuvwxyz'

res = "None"
for i in alphbet:
  if i not in S:
    res = i
    break
print(res)

Submission status: Accepted

Solution code:
import sys
import math
import collections
import itertools
import array
import inspect

# Set max recursion limit
sys.setrecursionlimit(10000)


# Debug output
def chkprint(*args):
    names = {
        id(v): k
        for k, v in inspect.currentframe().f_back.f_locals.items()
    }
    print(', '.join(
        names.get(id(arg), '???') + ' = ' + repr(arg) for arg in args))


# Binary converter
def to_bin(x):
    return bin(x)[2:]


def li_input():
    return [int(_) for _ in input().split()]


# --------------------------------------------

dp = None


def main():
    alphabets = "abcdefghijklmnopqrstuvwxyz"

    S = input()

    if len(set(S)) == 26:
        print("None")
        return

    for a in alphabets:
        if a not in S:
            print(a)
            return


main()

Submission status: Accepted

Solution code:
import sys
w=input()
alphabet=[chr(i) for i in range(97,97+26)]
for i in range (len(alphabet)):
    if w.count(alphabet[i])==0:
        print(alphabet[i])
        sys.exit()
print('None')

Submission status: Accepted

Solution code:
S = list( input())
alphabets = [ 0 for _ in range(26)]
for x in S:
    alphabets[ord(x)-97] = 1
ans = 'None'
for i in range(26):
    if alphabets[i] == 0:
        ans = chr(i+97)
        break
print(ans)

Submission status: Accepted

Solution code:
S = sorted(list(set(list(input()))))
test = sorted('abcdefghijklmnopqrstuvwxyz')

if S == test:
    print('None')

elif S[-1] == test[len(S)-1]:
    print(test[len(S)])

else:
    for num in range(len(S)):
        if test[num] != S[num]:
            print(test[num])
            break

Submission status: Accepted

Solution code:
S = sorted(list(set(list(input()))))
test = sorted('abcdefghijklmnopqrstuvwxyz')
ans = -1
if S == test:
    print('None')

elif S[-1] == test[len(S)-1]:
    print(test[len(S)])

else:
    for num in range(len(S)):
        if test[num] != S[num]:
            print(test[num])
            break

Submission status: Accepted

Solution code:
#71b
s = set(input())
diff = set('abcdefghijklmnopqrstuvwxyz')-s
if diff:
    print(sorted(diff)[0])
else:
    print('None')

Submission status: Accepted

Solution code:
def solve():
    s = input()
    s = set(s)
    dic = set(["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 = sorted(list(dic - s))
    if len(s) == 0:
        print("None")
        return
    print(s[0])


solve()

Submission status: Accepted

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

Submission status: Accepted

Solution code:
from collections import defaultdict
import sys,heapq,bisect,math,itertools,string,queue,datetime
sys.setrecursionlimit(10**8)
INF = float('inf')
mod = 10**9+7
eps = 10**-7
AtoZ = [chr(i) for i in range(65,65+26)]
atoz = [chr(i) for i in range(97,97+26)]

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

S = input()

for s in atoz:
	if not s in S:
		print(s)
		sys.exit()

print('None')

Submission status: Accepted

Solution code:

import sys
S = input()
d = {}
for i in range(26):
    d[i] = 0
for i in range(len(S)):
    d[ord(S[i]) - ord('a')] = 1

for i in range(26):
    if d[i] == 0:
        print(chr(ord('a') + i))
        sys.exit()

print("None")

Submission status: Accepted

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

def main():
    s = input()
    abc = [chr(i) for i in range(ord('a'), ord('a')+26)]
    
    for i in abc:
        if i not in s:
            print(i)
            exit()
    print('None')

if __name__ == '__main__':
    main()

Submission status: Accepted

Solution code:
s = set(input())
a = "abcdefghijklmnopqrstuvwxyz"
for i in s:
  a = a.replace(i, "")
if a:
  print(a[0])
else:
  print("None")

Submission status: Accepted

Solution code:
l=sorted({chr(97+i) for i in range(26)}^{i for i in input()})
if not l:
  print("None")
else:
  print(l[0])

Submission status: Accepted

Solution code:
ans = [0 for i in range(26)]
for c in input():
    ans[ord(c)-ord('a')] += 1
if ans.count(0)==0:
    print('None')
else:
    print(chr(ord('a')+ans.index(0)))

Submission status: Accepted

Solution code:
s=sorted(list(set(input())))
flag=True
for i in range(26):
  a=i+97
  if s.count(chr(a))==0:
    flag=False
    break
print('None' if flag else chr(a))

Submission status: Accepted

Solution code:
import sys
S = input()
target = 'abcdefghijklmnopqrstuvwxyz'
for chara in target:
  if chara in S:
    pass
  else:
    print(chara)
    sys.exit()
print('None')

Submission status: Accepted

Solution code:
S = input()
b =list('abcdefghijklmnopqrstuvwxyz')
c =[]
if len(set(S)) == len(b):
	print('None')
	exit()
for i in b:
    if i[0] not in S:
        print(i[0])
        exit()

Submission status: Accepted

Solution code:
s = raw_input()
ret = None
for x in "abcdefghijklmnopqrstuvwxyz"[::-1]:
	if x not in s:
		ret = x
print ret

Submission status: Accepted

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

albt = 'abcdefghijklmnopqrstuvwxyz'
for c in albt:
  if c not in s:
    print(c)
    exit()
print('None')

Submission status: Accepted

Solution code:
s = input()
from string import ascii_lowercase
t = set(ascii_lowercase)
a = t-set(s)
if len(a)==0:
  print("None")
else:
  print(sorted(a)[0])

Submission status: Accepted

Solution code:
S = input()
S_set = set(S)
alpha = set([chr(ord('a') + i) for i in range(26)])
ans = set(alpha - S_set)
ans = list(ans)
ans.sort()
if len(ans) >= 1:
	print(ans[0])
else:
	print("None")

Submission status: Accepted

Solution code:
al = list("abcdefghijklmnopqrstuvwxyz")
judge = "None"
S = list(input())
for i in range(26):
	if S.count(al[i]) == 0:
		judge = al[i]
		break

print(judge)

Submission status: Accepted

Solution code:
s=input()
ans=""
for i in range(97,123):
    ans+=chr(i)
for i in s:
    ans=ans.replace(i,"")
print(ans[0] if len(ans) else "None")

Submission status: Accepted

Solution code:
s = set(input())
ans = set(chr(x) for x in range(ord("a"), ord("z") + 1))

result = sorted(ans - s)
if result:
    print(result[0])
else:
    print("None")

Submission status: Accepted

Solution code:
N=[chr(i) for i in range(97,123)]
s=sorted(set(list(input())))
for i in N:
    if i  not in s:
        print(i)
        break
else:
    print("None")

Submission status: Accepted

Solution code:
import string
import sys
word = input()

for char in string.ascii_lowercase:
  if word.count(char) == 0:
    print(char)
    sys.exit()

print("None")
sys.exit()

Submission status: Accepted

Solution code:
"""
https://abc071.contest.atcoder.jp/tasks/abc071_b
"""
s=input()
e="abcdefghijklmnopqrstuvwxyz"
a=0
for i in range(len(e)):
    if s.find(e[i])==-1:
        print(e[i])
        break
    a=a+1
if a==len(e):
    print("None")

Submission status: Accepted

Solution code:

S=list(input())

ans=["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"]

S1=set(S)
ans1=set(ans)

ans_S=list(ans1-S1)
ans_S.sort()

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

Submission status: Accepted

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

Submission status: Accepted

Solution code:
s=input()
for c in range(ord('a'),ord('a')+26):
  al=chr(c)
  if(not al in s):
    print(al)
    exit()
print('None')

Submission status: Accepted

Solution code:
import sys

S = set(input())
alpha = 'abcdefghijklmnopqrstuvwxyz'

for al in alpha:
    if al not in S:
        print(al)
        sys.exit()
print('None')

Submission status: Accepted

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

Submission status: Accepted

Solution code:
from heapq import heappop
S = list(input())
Q = [chr(ord('a') + i) for i in range(26)]
while S:
    l = S.pop()
    if l in Q:
        Q.remove(l)
if Q:
    print(heappop(Q))
else:
    print("None")

Submission status: Accepted

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

S = list(input())

sorted_list = sorted(list(set(S)))
abc_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"]

for str1 in abc_list:
    if str1 not in sorted_list:
        print(str1)
        exit()
print("None")

Submission status: Accepted

Solution code:
S = list(input())

set_s = set(S)
set_all = set(list("abcdefghijklmnopqrstuvwxyz"))

set_diff = set_all - set_s

diff = []
for val in set_diff:
    diff.append(val)

ans = sorted(diff)

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

Submission status: Accepted

Solution code:
# input
S = 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', 'None']

for i in range(len(alphabet)):
    if alphabet[i] in S:
        continue
    else:
        print(alphabet[i])
        break

Submission status: Accepted

Solution code:
from collections import Counter
st = Counter(raw_input())
for c in 'abcdefghijklmnopqrstuvwxyz':
  if st[c] == 0:
    print c
    break
else:
  print 'None'

Submission status: Accepted

Solution code:
from collections import Counter
S = list(input())
A = list("abcdefghijklmenopqrstuvwxyz")


def ans(S):
    for a in A:
        if a not in S:
            return a
    return "None"


print(ans(S))

Submission status: Accepted

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

s = input()
A = {}
for i in range(len(s)):
    if s[i] not in A:
        A[s[i]] = True

for i in range(26):
    character = chr(ord('a')+i)
    if character not in A.keys():
        print(character)
        exit()

print('None')

Submission status: Accepted

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

Submission status: Accepted

Solution code:
S = input()

al = list("abcdefghijklmnopqrstuvwxyz")

for i in range(len(S)):
    try:
        al.remove(S[i])
    except:
        pass

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

Submission status: Accepted

Solution code:
S = input()
S_list = list(set(S))
al = 'abcdefghijklmnopqrstucwxyz'
al_list = list(al)
S_list.sort()
flg = 1
for i in range(len(al_list)):
    if al_list[i] in S_list:
        pass
    else:
        print(al_list[i])
        flg = 0
        break
    
if flg == 1:
    print('None')

Submission status: Accepted

Solution code:
S = input()

alphabet_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",
    ]

for s in S:
    if s in alphabet_list:
        alphabet_list.remove(s)
if len(alphabet_list) == 0:
    print("None")
else:
    print(alphabet_list[0])

Submission status: Accepted

Solution code:
S = "abcdefghijklmnopqrstuvwxyz"
input_S = input()
ans = []
for i in S:
    if i not in input_S:
        ans.append(i)
if not ans:
    print("None")
else:
    print(ans[0])

Submission status: Accepted

Solution code:
S = input()

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 alphabet in alphabets:
    flag = 1
    for character in S:
        if character == alphabet:
            flag = 0
    if alphabet == "z" and flag == 0:
        print("None")
    elif flag == 1:
        print(alphabet)
        break

Submission status: Accepted

Solution code:
import string
s=set(string.ascii_lowercase)-set(input())
print(min(s)if s else'None')

Submission status: Accepted

Solution code:
d = dict()
d['a'] = 1
d['b'] = 2
d['c'] = 3
d['d'] = 4
d['e'] = 5
d['f'] = 6
d['g'] = 7
d['h'] = 8
d['i'] = 9
d['j'] = 10
d['k'] = 11
d['l'] = 12
d['m'] = 13
d['n'] = 14
d['o'] = 15
d['p'] = 16
d['q'] = 17
d['r'] = 18
d['s'] = 19
d['t'] = 20
d['u'] = 21
d['v'] = 22
d['w'] = 23
d['x'] = 24
d['y'] = 25
d['z'] = 26

e = dict()
e[1] = 'a'
e[2] = 'b'
e[3] = 'c'
e[4] = 'd'
e[5] = 'e'
e[6] = 'f'
e[7] = 'g'
e[8] = 'h'
e[9] = 'i'
e[10] = 'j'
e[11] = 'k'
e[12] = 'l'
e[13] = 'm'
e[14] = 'n'
e[15] = 'o'
e[16] = 'p'
e[17] = 'q'
e[18] = 'r'
e[19] = 's'
e[20] = 't'
e[21] = 'u'
e[22] = 'v'
e[23] = 'w'
e[24] = 'x'
e[25] = 'y'
e[26] = 'z'

s =input()
lists = []
for i in range(len(s)):
    lists.append(d[s[i]])
lists.sort()
for i in range(1,28):
    if i != 27:
        if i not in lists:
            print(e[i])
            break
    else:
        print('None')

Submission status: Accepted

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

if len(set(s)) == 26:
    print("None")
else:
    alp = [chr(i) for i in range(97, 97+26)]
    for a in alp:
        if a not in sorted(set(s)):
            print(a)
            break

Submission status: Accepted

Solution code:
stringer = list("abcdefghijklmnopqrstuvwxyz")
strings = raw_input()

std = list(strings)

std.sort()
lister = {}

for j in range(len(stringer)):
    lister[stringer[j]]=0


for i in range(len(std)):
    count = lister[std[i]]
    lister[std[i]] = count + 1


hiter=0
for m in stringer:
    data = lister[m]
    if data == 0:
        hiter = m
        break

if hiter==0:
    print("None")
else:
    print(hiter)

Submission status: Accepted

Solution code:
S = 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"]
alphabet = "abcdefghijklmnopqrstuvwxyz"

ans = "None"
for i in range(len(alphabet)):
    if(alphabet[i] not in S):
        ans = alphabet[i]
        break
    
print(ans)

Submission status: Accepted

Solution code:
S = 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"]

ans = "None"
for i in range(len(alphabet)):
    if(alphabet[i] not in S):
        ans = alphabet[i]
        break
    
print(ans)

Submission status: Accepted

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

Submission status: Accepted

Solution code:
rec = set(list("abcdefghijklmnopqrstuvwxyz"))
rec2 = set()
s = input()
for i in range(len(s)):
    rec2.add(s[i])

t = sorted(list(rec - rec2))
if len(t) == 0:
    print("None")
else:
    print(t[0])

Submission status: Accepted

Solution code:
s=list(input())

for i in range(97,97+26):
  if chr(i) not in s:
    print(chr(i))
    break
else:
  print('None')

Submission status: Accepted

Solution code:
s = input()
alp = "abcdefghijklmnopqrstuvwxyz"

for i in range(len(s)):
    alp = alp.replace(s[i],"")
if alp != "":
    print(alp[0])
else:
    print("None")

Submission status: Accepted

Solution code:
S = raw_input()
lst = []
for i in range(0, 26):
	lst.append(True)

for i in range(0, len(S)):
	lst[ord(S[i])-97] = False

flag = True
for i in range(0, 26):
	if lst[i]:
		print chr(i+97)
		flag = False
		break

if flag:
	print 'None'

Submission status: Accepted

Solution code:
import string
S = set(input())
alpha = set(string.ascii_lowercase)
diff = alpha - S
if diff == set([]):
    print('None')
else:
    print(sorted(list(diff))[0])

Submission status: Accepted

Solution code:
a = "abcdefghijklmnopqrstuvwxyz"
S = input()
flg = 0
for i in a:
    if flg == 0 and i not in S:
        print(i)
        flg = 1
if flg == 0:
    print("None")

Submission status: Accepted

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

Submission status: Accepted

Solution code:
a = input()

b='abcdefghijklmnopqrstuvwxyz'
ans ='None'
for i in b:
    if i not in a:
        ans = i
        print(ans)
        break
if ans == 'None':
    print('None')

Submission status: Accepted

Solution code:
s = input()
c_lst = [0 for i in range(26)]

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

for i in range(len(c_lst)):
    if c_lst[i] == 0:
        print(chr(i+97))
        break
else:
    print("None")

Submission status: Accepted

Solution code:
s=input()
j=0
for a in 'abcdefghijklmnopqrstuvwxyz':
    if a not in s:
        j=1
        print(a)
        break
if j != 1:
    print('None')

Submission status: Accepted

Solution code:
S = input()
T = "abcdefghijklmnopqrstuvwxyz"
for t in T:
    if t not in S:
        print(t)
        break
else:
    print("None")

Submission status: Accepted

Solution code:
al = "abcdefghijklmnopqrstuvwxyz"
S1 = sorted(list(set(input())))
if (len(S1)==26):
    print("None")
else:
    for i in range (len(S1)):
        if al[i] != S1[i]:
            print(al[i])
            break
        elif i == len(S1)-1:
            print(al[len(S1)])
            break