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 = set([str(x) for x in input()])
A = "abcdefghijklmnopqrstuvwxyz"
for a in A:
    if a not in S:
        print(a)
        exit(0)
print("None")

Submission status: Accepted

Solution code:
def a():
    S = input()

    for i in range(97,123):
        c = chr(i)
        if c not in S:
            print(c)
            return
    print("None")
    
a()

Submission status: Accepted

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

for x in ss:
    if x not in s:
        print(x)
        exit()
print('None')

Submission status: Accepted

Solution code:
alphabet = ([chr(ord('a') + i) for i in range(26)])
str = input()
str = list(str)
ans = alphabet

for i in str:
    try:
        ans.remove(i)
    except:
        continue
try:
    print(ans[0])
except:
    print("None")

Submission status: Accepted

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

Submission status: Accepted

Solution code:
l = input()

ans = 'None'

for letter in 'abcdefghijklmnopqrstuvwxyz':
    if letter not in l:
        ans = letter
        break

print(ans)

Submission status: Accepted

Solution code:
cnt="abcdefghijklmnopqrstuvwxyz"
s=input()
ans=[0 for i in range(26)]

for i in range(len(s)):
  a=cnt.index(s[i])
  ans[a]+=1
res=30
for i in range(26):
  if ans[i]==0:
    res=i
    break
if res==30:
  print("None")
else:
  print(cnt[res])

Submission status: Accepted

Solution code:
s = list(input())
s = sorted(s)
a_z = list('abcdefghijklmnopqrstuvwxyz')
flag = 1
for x in range(len(a_z)):
    if a_z[x] in s:
        flag = 1
    else:
        print(a_z[x])
        flag = 0
        break
if flag:
    print("None")

Submission status: Accepted

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

tt = list(sorted(list('abcdefghijklmnopqrstuvwxyz')))
u = []
for i in tt:
    if not (i in s):
        u.append(i)
        
uu = list(sorted(u))

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

Submission status: Accepted

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

Submission status: Accepted

Solution code:
str_list = list(input())
import string
if set(str_list) == set(string.ascii_lowercase):
    print("None")
else:
    dif_list = sorted(list(set(string.ascii_lowercase) - set(str_list)))
    print(dif_list[0])

Submission status: Accepted

Solution code:
from string import ascii_lowercase

def first_not_in(s):
    for c in ascii_lowercase:
        if c not in s:
            return c
    return None

if __name__ == '__main__':
    print(first_not_in(input()))

Submission status: Accepted

Solution code:
import sys

stdin = sys.stdin

ni = lambda: int(ns())
na = lambda: list(map(int, stdin.readline().split()))
ns = lambda: stdin.readline().strip()

s = ns()
alfa = [chr(i) for i in range(97,123)]
ans = [chr(i) for i in range(97,123)]
for i in s:
    if i in alfa:
        if i in ans:
            ans.remove(i)

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

Submission status: Accepted

Solution code:
import string

s = input()
if len(set(s)) == 26: print('None')
else:
    for c in string.ascii_lowercase:
        if c not in s:
            print(c)
            break

Submission status: Accepted

Solution code:
import string
s = input()
dic = dict()
for c in s:
    dic[c] = 1
for i in range(len(string.ascii_lowercase)):
    c = string.ascii_lowercase[i]
    if not(c in dic):
        print(c)
        exit()
print('None')

Submission status: Accepted

Solution code:
ls = [chr(ord('a')+num) for num in range(26)]
s = input()
for x in range(len(ls)):
    if ls[x] not in s:
        print(ls[x])
        break
else:
    print("None")

Submission status: Accepted

Solution code:
import math
import sys

def getinputdata():

    # 配列初期化
    array_result = []
    
    data = input()

    
    array_result.append(data.split(" "))

    flg = 1

    try:


        while flg:

            data = input()

            array_temp = []

            if(data != ""):
                
                array_result.append(data.split(" "))

                flg = 1

            else:

                flg = 0
    finally:


        return array_result





arr_data = getinputdata()

s = arr_data[0][0]

str="abcdefghijklmnopqrstuvwxyz"

for v in str:
    
#    print(v)
    
    if v not in s:
        
        print(v)
        
        break
else:
    print("None")

Submission status: Accepted

Solution code:
S = input()
exist = set()
for i in S:
    exist.add(i)
for j in "abcdefghijklmnopqrstuvwxyz":
    if j not in exist:
        print(j)
        exit()
print("None")

Submission status: Accepted

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

Submission status: Accepted

Solution code:
S = set(input())
for alpha in "abcdefghijklmnopqrstuvwxyz":
    if alpha in S:
        pass
    else:
        print(alpha)
        break
else:
    print(None)

Submission status: Accepted

Solution code:
from collections import Counter
import string

S = input()
count = Counter(list(S))

found = False
for ch in string.ascii_lowercase:
    if count[ch] == 0:
        print(ch)
        exit()

if not found:
    print('None')

Submission status: Accepted

Solution code:
s = input()
a,num = "abcdefghijklmnopqrstuvwxyz",0
for i in range(26):
	if s.count(a[i])==0:
		print(a[i])
		break
	else:
		num += 1
if num==26:
	print("None")

Submission status: Accepted

Solution code:
# coding: utf-8
a=set("qazwsxedcrfvtgbyhnujmikolp")
b=set(input())
print(sorted(a-b)[0] if len(a-b)>0 else 'None')

Submission status: Accepted

Solution code:
data=input()
temp=[chr(97+i) for i in range(26)]
for i in range(len(data)):
    temp[ord(data[i])-97]=0
cnt=26
for i in range(26):
    if temp[i]!=0:
        cnt=i
        break
if cnt<=25:print(temp[cnt])
else:print("None")

Submission status: Accepted

Solution code:
import sys;
print((sorted(set([chr(i) for i in range(ord('a'),ord('z')+1)])-set(sys.stdin.readline()))+[None])[0])

Submission status: Accepted

Solution code:
import sys
print((sorted(set([chr(i) for i in range(97,123)]) - set(sys.stdin.readline())) + [None])[0])

Submission status: Accepted

Solution code:
s=input()
for x in list('abcdefghijklmnopqrstuvwxyz'):
    if s.count(x)==0:print(x);exit()
print('None')

Submission status: Accepted

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

# AtCoder Beginner Contest
# Problem B

if __name__ == '__main__':
    S = sorted(set(list(input())))
    alphabets = [chr(ord('a') + i) for i in range(26)]

    if len(S) == 26:
        print('None')
    else:
        for alphabet in alphabets:
            if alphabet not in S:
                print(alphabet)
                break

Submission status: Accepted

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

# AtCoder Beginner Contest
# Problem B

if __name__ == '__main__':
    S = sorted(set(list(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']

    if len(S) == 26:
        print('None')
    else:
        for alphabet in alphabets:
            if alphabet not in S:
                print(alphabet)
                break

Submission status: Accepted

Solution code:
S = input()
alpha = [chr(ord('a')+i) for i in range(26)]
for i in range(len(S)):
  if S[i] in alpha:
    alpha.pop(alpha.index(S[i]))
if len(alpha) > 0:
  print(alpha[0])
else:
  print('None')

Submission status: Accepted

Solution code:
#!/usr/bin/env python
s = input()
ans = set('abcdefghijklmnopqrstuvwxyz')-set(s)
if len(ans)==0:
    print('None')
else:
    print(min(ans))

Submission status: Accepted

Solution code:
s = input()
not_exists = []
for c in range(97, 123):
    if chr(c) not in s:
        not_exists.append(chr(c))
        print(chr(c))
        break
if len(not_exists) == 0:
    print('None')

Submission status: Accepted

Solution code:
s=input()
exist=[False for i in range(26)]

for c in s:
	exist[ord(c)-ord('a')]=True
for i in range(26):
	if not exist[i]:
		print(chr(ord('a')+i))
		break
else:
	print("None")

Submission status: Accepted

Solution code:
S = input()

s_char = [c for c in S]
alphas = [chr(i) for i in range(97, 97 + 26)]

for alpha in alphas:
    if alpha not in s_char:
        print(alpha)
        exit()
print("None")

Submission status: Accepted

Solution code:
alphabet = "abcdefghijklmnnopqrstuvwxyz"
def solve():
    s = input()
    for i in alphabet:
        if i not in s:
            print(i)
            break
    else:
        print("None")
solve()

Submission status: Accepted

Solution code:
import string
S = str(input())
a = set(S)
b = set(string.ascii_lowercase)
c = b - a
if len(list(c)) == 0:
    print(None)
else:
    print(sorted(list(c))[0])

Submission status: Accepted

Solution code:
s = input()
ch = {chr(i) for i in range(ord('a'), ord('z')+1)}
ss = set()
for i in range(len(s)): ss.add(s[i])
tmp = sorted(list(ch ^ ss))
print(tmp[0] if len(tmp) else "None")

Submission status: Accepted

Solution code:
S=sorted(list(set(list(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"]
sum=0
A="None"
for i in range(len(S)):
    if S[i]!=alph[i]:
        A=alph[i]
        break
if A=="None" and len(S)<26:
    A=alph[i+1]

print(A)

Submission status: Accepted

Solution code:
s=input()
l=[]
for i in s:
    l.append(i)
l.sort()
li=[]
for i in range(len(l)-1):
    if(l[i]!=l[i+1]):
        li.append(l[i])
li.append(l[-1])
alph="abcdefghijklmnopqrstuvwxyz"
for i in li:
    for j in range(len(alph)):
        if(i==alph[j]):
            alph=alph.replace(i,"")
            break
if(len(alph)==0):
    print("None")
else:
    print(alph[0])

Submission status: Accepted

Solution code:
import sys
S = input()
alphabet = []
for i in range(97,97+26):
    alphabet.append(chr(i))
for i in range(len(alphabet)):
    if not alphabet[i] in S :
        print(alphabet[i])
        sys.exit()
print("None")

Submission status: Accepted

Solution code:
s = input()
ls = []
nflag = False
for i in range(len(s)):
    ls.append(s[i])

for i in range(26):
    if not chr(i+97) in ls:
        print(chr(i+97))
        nflag = True
        break

if not nflag:
    print('None')

Submission status: Accepted

Solution code:
S=set(input())
Sl=list(S)
Sl.sort()
moji=["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"]
T="None"
for i in range(len(Sl)):
    if Sl[i]!=moji[i]:
        T=moji[i]
        break

if T=="None" and len(Sl)<26:
    T=moji[i+1]

print(T)

Submission status: Accepted

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

Submission status: Accepted

Solution code:
lis = ["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"]
n = list(input())
k = 0
while 1:
  if lis[k] not in n:
    print(lis[k])
    break
  k += 1

Submission status: Accepted

Solution code:
import string
xs = input()


def foo(xs):
    a = string.ascii_lowercase
    cnt = [0] * len(a)
    for x in xs:
        cnt[ord(x) - ord('a')] += 1

    for i, c in enumerate(cnt):
         if c == 0:
            print(a[i])
            return
    print("None")
    return


foo(xs)

Submission status: Accepted

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

for c in t:
   if c not in s:
      print(c)
      exit()

print("None")

Submission status: Accepted

Solution code:
ans = "abcdefghijklmnopqrstuvwxyz"
for c in input():
    ans = ans.replace(c, '')
if len(ans) == 0:
    print("None")
else:
    print(ans[0])

Submission status: Accepted

Solution code:
s = set(input())
for c in list("abcdefghijklmnopqrstuvwxyz"):
    if c not in s:
        print(c)
        exit()
print("None")

Submission status: Accepted

Solution code:
dic = 'abcdefghijklmnopqrstuvwxyz'
s = input()
import sys
for d in dic:
    if d not in s:
        print(d)
        sys.exit(0)
print('None')

Submission status: Accepted

Solution code:
# main関数
if __name__ == '__main__':

    S = input()
    flag = True
    for i in range(26):
        target = chr(ord('a') + i)
        if S.find(target) == -1:
            print(target);
            flag = False
            break

    if flag :
        print("None")

Submission status: Accepted

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

al=list('abcdefghijklmnopqrstuvwxyz')

r=list(set(al)-set(s))
r.sort()

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

Submission status: Accepted

Solution code:
s=list(set(input()))
test=["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"]
test.sort()
s.sort()
if len(s)==len(test):
    print("None")
    exit()

i=0
while True:
    if len(s)<=i:
        print(test[i])
        break
        
    if test[i]!=s[i]:
        print(test[i])
        break
    i+=1

Submission status: Accepted

Solution code:
import string

s = input()
for c in string.ascii_lowercase:
  if c not in s:
    print(c)
    exit()
print('None')

Submission status: Accepted

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

Submission status: Accepted

Solution code:
print((sorted(set("aquickbrownfoxjumpsoverthelazydog")-set(input()))+["None"])[0])

Submission status: Accepted

Solution code:
#!/usr/bin/env python

s = list(input())

answer = "None"
for n in range(ord("a"), ord("a") + 26):
    ch = chr(n)
    if not ch in s:
        answer = ch
        break
print(answer)

Submission status: Accepted

Solution code:
alphabet = "abcdefghijklmnnopqrstuvwxyz"

def solve():
	S = input()
	for c in alphabet:
		if c not in S:
			print(c)
			exit()
	print("None")
	exit()
			
			
solve()

Submission status: Accepted

Solution code:
S=input()
ans='None'
for c in range(26):
  if chr(97+c) not in S:
    ans = chr(97+c)
    break
print(ans)

Submission status: Accepted

Solution code:
s = 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:
alphabet = "abcdefghijklmnopqrstuvwxyz"

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

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"
alp = list(map(str, alp.split()))
s = input()
for i in range(len(s)):
    for j in range(26):
        if(s[i] == alp[j]):
            alp[j] = "?"
while("?" in alp):
    alp.remove("?")
if(len(alp) == 0):
    print("None")
else:
    print(alp[0])

Submission status: Accepted

Solution code:
import string
s = input()
for c in string.ascii_lowercase:
    if c not in s:
        print(c)
        exit()
print("None")

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))
        exit()
print('None')

Submission status: Accepted

Solution code:
s = raw_input()
f = False
for x in 'abcdefghijklmnopqrstuvwxyz':
	if x not in s:
		print x
		f = True
		break
if not f:
	print 'None'

Submission status: Accepted

Solution code:
S = list(input())

result = "None"
for i in range(26):
    if chr(97 + i) not in S:
        result = chr(97 + i)
        break
print(result)

Submission status: Accepted

Solution code:
import string
res = sorted(set(string.ascii_lowercase) - set(input()))
print(res[0] if res else "None")

Submission status: Accepted

Solution code:
val = list(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"]

val2 = set(val)
for i in val2:
    if i in alp:
        alp.remove(i)
try:
    print(alp[0])
except IndexError:
    print("None")

Submission status: Accepted

Solution code:
s=input()
d=[0 for i in range(26)]
for i in range(len(s)):
  d[ord(s[i])-ord("a")]+=1
ss="None"
for i in range(26):
 if d[i]==0:
    ss=chr(i+ord("a"))
    break
print(ss)

Submission status: Accepted

Solution code:
import string
 
S = set(list(input()))
ans = set(list(string.ascii_lowercase)) - S
if len(ans) == 0:
    print("None")
    exit()
ans = sorted(list(ans))[0]
print(ans)

Submission status: Accepted

Solution code:
S = input()

N = "None"
count = 0
app = [0] * 26
for i in range(len(S)):
    app[ord(S[i]) - ord("a")] = 1

for i in range(26):
    if app[i] == 1:
        count += 1
        if count == 26:
            print(N)

    if app[i] == 0:
        print (chr(i + ord("a")))
        break

Submission status: Accepted

Solution code:
import string

S = set(list(input()))
ans = set(list(string.ascii_lowercase)) - S
if len(ans) == 0:
    print("None")
    exit()
ans = sorted(list(ans))[0]
print(ans)

Submission status: Accepted

Solution code:
S = raw_input()
for c in [chr(ord("a") + i) for i in xrange(26)]:
    if c in S:
        continue
    else:
        print c
        break
else:
    print "None"

Submission status: Accepted

Solution code:
#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import string

def main():
    S = set(input())
    T = set(string.ascii_lowercase)

    T -= S
    if not T:
        print("None")
    else:
        print(sorted(T)[0])

if __name__ == "__main__": main()

Submission status: Accepted

Solution code:
abc = 'abcdefghijklmnopqrstuvwxyz'
S = input()
for x in abc:
    if not x in S:
        print(x)
        break
else:
    print('None')

Submission status: Accepted

Solution code:
n = input()
for i in range(26):
    c = chr(i+ord("a"))
    if not c in n: print(c); break
else: print("None")

Submission status: Accepted

Solution code:
if __name__ == '__main__':
    S = input()
    dic = [chr(i) for i in range(97, 123)]
    j=0
    for i in range(len(dic)):
        if dic[i] not in S:
            j = 1
            print(dic[i])
            break
    if j == 0:
        print('None')

Submission status: Accepted

Solution code:
import string
S = input()
for a in string.ascii_lowercase:
    if a not in S:
        print(a)
        exit(0)
print('None')

Submission status: Accepted

Solution code:
a=raw_input()
for i in range(97,123):
 if chr(i) not in a:
  print chr(i)
  exit()
print "None"

Submission status: Accepted

Solution code:
S = input()
alphabet = "abcdefghijklmnopqrstuvwxyz"
found = False
for i in alphabet:
  if i not in S:
    print(i)
    found = True
    break

if not found:
    print('None')

Submission status: Accepted

Solution code:
S = input()
alphabet = "abcdefghijklmnopqrstuvwxyz"
found = [i for i in alphabet if i not in S]
found.sort()
if len(found) == 0:
  print('None')
else:
  print(found[0])

Submission status: Accepted

Solution code:
s = list(input().strip())
s.sort()
i = 0
for c in "abcdefghijklmnopqrstuvwxyz!":
    if i < len(s) and s[i] == c:
        while i < len(s) and s[i] == c:
            i += 1
    else:
        if c != "!":
            print(c)
        else:
            print("None")
        raise SystemExit

Submission status: Accepted

Solution code:
S = set(input())
sort = sorted(S)
e = 'no'
for i in range(97, 123):
    if chr(i) not in sort:
        print(chr(i))
        e = 'yes'
        break
if e == 'no':
    print('None')

Submission status: Accepted

Solution code:
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools
 
sys.setrecursionlimit(10**7)
inf = 10**20
gosa = 1.0 / 10**10
mod = 10**9 + 7
 
def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()
 
 
def main():
    c = collections.Counter(S())
    for k in string.ascii_lowercase:
        if c[k] == 0:
            return k
    return 'None'
 
print(main())

Submission status: Accepted

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

Submission status: Accepted

Solution code:
# -*- encoding: utf-8 -*-
s = list(input().rstrip())
alpha = list(map(chr, range(ord('a'), ord('z') + 1)))

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

Submission status: Accepted

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

Submission status: Accepted

Solution code:
from collections import defaultdict
from itertools import product, groupby
from math import pi
from collections import deque
from bisect import bisect, bisect_left, bisect_right
from string import ascii_lowercase
INF = 10 ** 10


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



if __name__ == '__main__':
    main()

Submission status: Accepted

Solution code:
s=list(input())
L=[]
for t in range(0,26):
    if chr(97+t) not in s:
        a=chr(97+t)
        L.append(a)
        
if not L:
    print("None")
else:
    print(L[0])

Submission status: Accepted

Solution code:
all_char = map(chr,range(97,123))
all_set = set(all_char)
input_set = set(input())
print(min(all_set-input_set or{"None"}))

Submission status: Accepted

Solution code:
s = input()
swi = 0
lst = ["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 (lst[i] in s) == False:
        print(lst[i])
        swi = 1
        break
if swi == 0:
    print("None")

Submission status: Accepted

Solution code:
print((lambda s:next((chr(i)for i in range(97,123)if chr(i)not in s),"None"))(input()))

Submission status: Accepted

Solution code:
print(min(set(chr(97+i)for i in range(26))-set(input())or["None"]))

Submission status: Accepted

Solution code:
print((lambda s:next((c for c in map(chr,range(97,123))if c not in s),"None"))(input()))

Submission status: Accepted

Solution code:
print(min([set(chr(97+i)for i in range(26))-set(input())or["None"]][0]))

Submission status: Accepted

Solution code:
print([sorted(set(chr(97+i)for i in range(26))-set(input()))or["None"]][0][0])

Submission status: Accepted

Solution code:
x=set(chr(97+i) for i in range(26))-set(input())
print("None" if not x else min(x))

Submission status: Accepted

Solution code:
print((lambda x:"None" if not x else min(x))(set(chr(97+i) for i in range(26))-set(input())))

Submission status: Accepted

Solution code:
print((lambda x:"None" if not x else x[0])(sorted(set(chr(97+i) for i in range(26))-set(input()))))

Submission status: Accepted

Solution code:
x=sorted(set(chr(97+i) for i in range(26))-set(input()))
print("None" if not x else x[0])

Submission status: Accepted

Solution code:
print((lambda x:"None" if not x else x[0])(sorted(set(chr(97+i) for i in range(26))-set(list(input())))))

Submission status: Accepted

Solution code:
print((lambda x:"None" if not x else x[0])(sorted(list(set(chr(i) for i in range(97,97+26))-set(input())))))

Submission status: Accepted

Solution code:
print((lambda x:"None" if not x else x[0])(sorted(list(set([chr(i) for i in range(97, 97+26)]) - set(list(input()))))))

Submission status: Accepted

Solution code:
x=set([chr(i) for i in range(97,97+26)])-set(list(input()))
print("None" if not x else sorted(list(x))[0])

Submission status: Accepted

Solution code:
print((lambda x:"None" if not x else sorted(list(x))[0])(set([chr(i) for i in range(97,97+26)])-set(list(input()))))

Submission status: Accepted

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

def main():
    alphabets = 'abcdefghijklmnopqrstuvwxyz'
    text = input().strip()

    result = 'None'
    for c in alphabets:
        if c not in text:
            result = c
            break
    print(result)


if __name__ == '__main__':
    main()

Submission status: Accepted

Solution code:
bun=input()
mm="abcdefghijklmnopqrstuvwxyz"
for x in range(len(mm)):
    if mm[x] not in bun:
        print(mm[x])
        break
else:
    print("None")

Submission status: Accepted

Solution code:
import string


def main():
    cs = set(input())
    print(solve(cs))


def solve(cs):
    for c in string.ascii_lowercase:
        if c not in cs:
            return c
    return 'None'


if __name__ == '__main__':
    main()

Submission status: Accepted

Solution code:
S = 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()

a = 0
for i in range(97, 97 + 26):
    if chr(i) not in S:
        print(chr(i))
        a = 1
        break

if a == 0:
    print('None')

Submission status: Accepted

Solution code:
import collections
s = collections.Counter('abcdefghijklmnopqrstuvwxyz')
l = collections.Counter(input())
ret = 'None'
for el in sorted((s+l).items()):
  if el[1] == 1:
    ret = el[0]
    break
print(ret)

Submission status: Accepted

Solution code:
S = input()
alphabet = "abcdefghijklmnopqrstuvwxyz"

for alp in alphabet:
    if alp not in S:
        print(alp)
        break
else:
    print("None")

Submission status: Accepted

Solution code:
s = input()

l = [chr(i) for i in range(97, 97+26)]
# print(l)

for v in l:
	if v in s:
		if v == "z":
			print("None")
			break
	else:
		print(v)
		break

Submission status: Accepted

Solution code:
def solve(): # 071B - Not Found
    alphabet = []
    for i in range(26):
        alphabet.append(chr(97 + i))
    s = list(input())

    for j in s:
        if j in alphabet:
            alphabet.remove(j)
        else:
            pass

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


solve()

Submission status: Accepted

Solution code:
S = input()

for i in range(ord('a'), ord('z') + 1):
    if chr(i) not in S:
        print(chr(i))
        break
else:
    print('None')

Submission status: Accepted

Solution code:
import sys
line = raw_input()
res = dict()
for i in line:
    res[i] = 1
    if len(res) == 26:
        print 'None'
        sys.exit(0)
for i in 'abcdefghijklmnopqrstuvwxyz':
    if res.get(i, None) is None:
        print i
        sys.exit(0)

Submission status: Accepted

Solution code:
S = set(raw_input())
T = set([chr(i) for i in range(ord('a'), ord('z')+1)])
U = T - S
print "None" if len(U) == 0 else sorted(list(U))[0]

Submission status: Accepted

Solution code:
import sys

str = sys.stdin.read()
words = "abcdefghijklmnopqrstuvwxyz"
wordslist= list(words)
list2 = list(words)
try:
    for item in wordslist:
        iss = str.find(item)
        if iss != -1:
            list2.remove(item)
except Exception:
    pass

if len(list2) == 0:
    print("None")
else:
    print(list2[0])

Submission status: Accepted

Solution code:
import sys

alphabet = "abcdefghijklmnopqrstuvwxyz"
word = raw_input()
found = 0

for letter in alphabet:
    if letter not in word:
        print letter
        found = 1
        break

if found == 0:
    print "None"

Submission status: Accepted

Solution code:

S = input()
res = "None"

for c in range(26):
    if chr(ord('a') + c) not in S:
        res = chr(ord('a') + c)
        break
print(res)

Submission status: Accepted

Solution code:
import string
import sys

S = input()
l = string.ascii_lowercase

for c in l:
  there = False
  for cs in S:
    if c == cs:
      there = True
  if there == False:
    print(c)
    sys.exit()

print("None")
sys.exit()

Submission status: Accepted

Solution code:
S = str(input())
alphabet = "abcdefghijklmnopqrstuvwxyz"

flag = [0] * 26
for i in range(26):
    if alphabet[i] in S:
        flag[i] = 1

for i in range(26):
    if flag[i] == 0:
        print(alphabet[i])
        break

if flag == [1] * 26:
    print("None")

Submission status: Accepted

Solution code:
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools

sys.setrecursionlimit(10**7)
inf = 10**20
gosa = 1.0 / 10**10
mod = 10**9 + 7

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()


def main():
    c = collections.Counter(S())
    for k in string.ascii_lowercase:
        if c[k] == 0:
            return k
    return 'None'

print(main())

Submission status: Accepted

Solution code:
al = set([chr(97 + i) for i in range(26)])
inp = set([x for x in input()])

mal = al.difference(inp)

if len(mal):
    print(chr(min(map(ord,mal))))
else:
    print("None")

Submission status: Accepted

Solution code:
#! /bin/python
# coding:utf-8

import sys

def strchr(string, char):
	for token in string:
		if (token == char):
			return 1
	return 0

S = raw_input()

tmp = chr(ord('a'))
for i in range(0, 26):
	if (strchr(S, tmp) == 0):
		print tmp
		sys.exit()
	tmp = chr(ord(tmp) + 1)

print "None"

Submission status: Accepted

Solution code:
# coding: utf-8
# Here your code !
s = set(input())
ab = {chr(i) for i in range(97,97+26)}
ab -= s
if len(ab) == 0:
    print("None")
else:
    print(min(ab))

Submission status: Accepted

Solution code:
S = input()
check = list("abcdefghijklmnopqrstuvwxyz")

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

Submission status: Accepted

Solution code:
from string import ascii_lowercase

s = set(input())
t = set(ascii_lowercase)

if len(s) == 26:
    print("None")
else:
    print(sorted(t - s)[0])

Submission status: Accepted

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

for x in l:
    if not x in S:
        print(x)
        exit()
        
print('None')

Submission status: Accepted

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

for x in l:
    if not x in S:
        print(x)
        break
    else:
        if x == 'z':
            print('None')