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:
dic = {}
for n in range(ord("a"), ord("z")+1):
    dic[chr(n)] = 0
s = input()
for l in s:
    dic[l] += 1

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

Submission status: Accepted

Solution code:
s = input()
xs = "abcdefghijklmnopqrstuvwxyz"
for a in s:
    xs = xs.replace(a, "", 1)
try:
    print(xs[0])
except:
    print("None")

Submission status: Accepted

Solution code:
S = set(input())
if len(S) == 26:
    print('None')
else:
    exclude = set('abcdefghijklmnopqrstuvwxyz')
    print(sorted(exclude - S)[0])

Submission status: Accepted

Solution code:
S = input()
S = list(S)
S = set(S)
S = list(S)
S.sort()
alpabet = 'abcdefghijklmnopqrstuvwxyz'
alphabet = list(alpabet)
count = 0
judge = 0

if(len(S) == 26):
  print('None')
else:
  for i in range(len(S)):
   count += 1
   if(S[i] != alphabet[i]):
      print(alphabet[i])
      judge = 1
      break
  if((count == len(S))and(judge==0)):
    print(alphabet[count])

Submission status: Accepted

Solution code:
S = raw_input()

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

Submission status: Accepted

Solution code:
s = input()
baket = {}
answer = 'None'
for i in range(97, 97+26):
  baket[chr(i)] = 0
for j in s:
  baket[j] += 1
for i in range(97, 97+26):
  if baket[chr(i)] == 0:
    answer = chr(i)
    break
print(answer)

Submission status: Accepted

Solution code:
from statistics import mean, median,variance,stdev
import numpy as np
import sys
import math
import fractions
import itertools

def j(q):
    if q==1: print("Yes")
    else:print("No")
    exit(0)


def ct(x,y):
    if (x>y):print("")
    elif (x<y): print("")
    else: print("")

def ip():
    return int(input())

def swap(s,pos):
    s[pos]-=1
    s[pos+1]+=1
    print(s)
    if pos == n-2: return s
    if s[pos+2] == 0: swap(s,pos+1)
    return s

pl = 'abcdefghijklmnopqrstuvwxyz'

#n = ip()                              #入力整数1つ
#h,w= (int(i) for i in input().split())      #入力整数横2つ
#n,x,y = (int(i) for i in input().split())    #入力整数横3つ
#n,m,x,y= (int(i) for i in input().split())  #入力整数横4つ
#a = [int(i) for i in input().split()]        #入力整数配列
a = input()                                  #入力文字列
#a = input().split()                          #入力文字配列
#n = ip()                      #入力セット(整数改行あり)(1/2)
#a=[ip() for i in range(n)]    #入力セット(整数改行あり)(2/2)

#jの変数はしようできないので注意
#全足しにsum変数使用はsum関数使用できないので注意
l = [pl[i] for i in range(26)]
for i in range(len(a)):
    if a[i] in l:
        p  = l.index(a[i])
        l.pop(p)
if len(l)==0:
    print("None")
else :
    print(l[0])

Submission status: Accepted

Solution code:
#abc071_b
s=str(input())
s_l=set(s)
alphabet="abcdefghijklmnopqrstuvwxyz"
alpha_l=set(alphabet)
l=alpha_l-s_l
l=sorted(l)

if not l:
	print("None")
else:
	ans=l[0]
	print(l[0])

Submission status: Accepted

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

print(sorted(abc - S)[0] if len(abc - S) != 0 else None)

Submission status: Accepted

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

Submission status: Accepted

Solution code:
s = input()
s = sorted(s)
a = "abcdefghijklmnopqrstuvwxyz"
for i in range(len(a)):
  if a[i] not in s:
    print(a[i])
    exit()
print("None")

Submission status: Accepted

Solution code:
import sys
s=input()
a='abcdefghijklmnopqrstuvwxyz'
for i in a:
    if s.find(i) == -1:
        print(i)
        sys.exit()
print('None')

Submission status: Accepted

Solution code:
s=list(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"]
for x in a:
    if not x in s:
        print(x)
        exit()
print("None")

Submission status: Accepted

Solution code:
S = sorted(set(list(input())))
ABC = [chr(c) for c in range(ord('a'), ord('a') + 26)]
if S != ABC :
    for i in range(27) :
        try :
            if S[i] != ABC[i] :
                print(ABC[i])
                break
        except :
            print(ABC[i])
            break
else :
    print("None")

Submission status: Accepted

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

flag = False
for s in alp:
    if s not in S:
        print(s)
        flag = True
        break
if not flag:
    print('None')

Submission status: Accepted

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

for i in abc:
    if not s.count(i) == 1:
        ans = i
        break
else:
    ans = "None"

print(ans)

Submission status: Accepted

Solution code:
s = sorted(input())
alphabet = "abcdefghijklmnopqrstuvwxyz"
flag = 0
for t in alphabet:
  if s.count(t) == 0:
    print(t)
    break
  else:flag += 1

if flag ==26:print("None")

Submission status: Accepted

Solution code:
# 072B
s = sorted(set(input()))
abc = 'abcdefghijklmnopqrstuvwxyz'
for a in abc:
    if s.count(a)==0:
        print(a)
        break
else:
    print('None')

Submission status: Accepted

Solution code:
S = input()
alp = 'abcdefghijklmnopqrstuvwxyz'
for s in S:
  if(s in alp):
    alp = alp.replace(s, '')
if(alp == ''):
  print('None')
else:
  print(alp[0])

Submission status: Accepted

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

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
    if i==ord('z'):
        print('None')

Submission status: Accepted

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

Submission status: Accepted

Solution code:
import string
S=input()
A=string.ascii_lowercase
B=list(set(A)-set(S))
B.sort()
print(B[0] if B else 'None')

Submission status: Accepted

Solution code:
import sys
a=[0]*26
s=input()
for i in range(len(s)):
    a[ord(s[i])-97]=1
    #print(a)
    if 0 not in a:
        print('None')
        sys.exit(0)
for i in range(26):
    #print(i)
    if a[i]==0:
        print(chr(i+97))
        break

Submission status: Accepted

Solution code:
import string
S = list(input().rstrip())
S.sort()
t = set(S)
if len(t) == 26: print('None')
else:
    for u in string.ascii_lowercase:
        if not u in t:
            print(u)
            break

Submission status: Accepted

Solution code:
s = set(input())
on = set("abcdefghijklmnopqrstuvwxyz")
try:
  print(min(on-s))
except ValueError:
  print("None")

Submission status: Accepted

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

Submission status: Accepted

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

Submission status: Accepted

Solution code:
s = set(input())
t = set('abcdefghijklmnopqrstuvwxyz')
ans = sorted(list(s ^ t))
print(ans[0] if len(ans) != 0 else 'None')

Submission status: Accepted

Solution code:
alphabets = [i for i in range(ord('a'), ord('z') + 1)]
lists = [ord(i) for i in input()]
lists=list(set(lists))
lists.sort()
for i in range(len(alphabets)):
    if i+1>=len(lists) and i!=25:
        if alphabets[i] == lists[i]:
            print(chr(alphabets[i+1]))
            exit(0)
    if alphabets[i]!=lists[i]:
        print(chr(alphabets[i]))
        exit(0)


print('None')

Submission status: Accepted

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

Submission status: Accepted

Solution code:
s = input()

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

Submission status: Accepted

Solution code:
A=input()
chars = list(A)
#print(chars)
i=97
while chars.count(chr(i))>0 and i<(97+26):
    i=i+1
if i<(97+26):
    print(chr(i))
else:
    print("None")

Submission status: Accepted

Solution code:
S = input()

unko =["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 unko:
    if S.count(i) == 0:
        print(i)
        exit()

print("None")

Submission status: Accepted

Solution code:
A=input()
B=list("abcdefghijklmnopqrstuvwxyz")
for i in range(26):
  if not B[i]  in A:
    print(B[i])
    exit()
print("None")

Submission status: Accepted

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

Submission status: Accepted

Solution code:
str_s = input()

all = set([chr(i) for i in range(97, 97+26)])
inputs = set(list(str_s))

diff = all.difference(inputs)

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

Submission status: Accepted

Solution code:
import string
x = input()
def func(x):
    diff = set(string.ascii_lowercase)- set(x)
  
    if diff:
        print(sorted(diff)[0])
    else:
        print('None')
        
func(x)

Submission status: Accepted

Solution code:
s=input()

al="abcdefghijklmnopqrstuvwxyz"
ishoge = False

for a in al:
    isExist = False
    for char in s:
        if a==char:
            isExist = True
            break
            
    if not isExist:
        print(a)
        ishoge = True
        break
        
if not ishoge:
    print("None")

Submission status: Accepted

Solution code:
S = input()
s = set()
table = "abcdefghijklmnopqrstuvwxyz"
for x in S:
  s.add(x)
v = 0
for x in table:
  if x not in s:
    print(x)
    v = 1
    break
  else:
    pass
if v == 0:
  print("None")

Submission status: Accepted

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

for a in 'abcdefghijklmnopqrstuvwxyz':
    if a not in s:
        print(a)
        break
else:
    print('None')

Submission status: Accepted

Solution code:
*s, = map(ord, list(input()))
s = set(s)

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

Submission status: Accepted

Solution code:
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"]
s = str(input())
for i in range(len(s)):
    if s[i] in alphabet:
        m = alphabet.index(s[i])
        del alphabet[m]
    if alphabet == []:
        print("None")
        exit()
print(alphabet[0])

Submission status: Accepted

Solution code:
import string


def main():
    s = input()
    for si in string.ascii_lowercase:
        if si not in s:
            print(si)
            break
    else:
        print("None")


if __name__ == '__main__':
    main()

Submission status: Accepted

Solution code:
import string
n = input()
s = set(string.ascii_lowercase) - set(n)

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

Submission status: Accepted

Solution code:
s = list(input())
s_ = list('abcdefghijklmnopqrstuvwxyz')

s = list(set(s))
s.sort()

for i in range(len(s)):
    if s[i] != s_[i]:
        print(s_[i])
        exit()
if len(s) < 26: print(s_[len(s)])
else: print('None')

Submission status: Accepted

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

if d - s == set():
    print('None')
else:
    print(sorted(d - s)[0])

Submission status: Accepted

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

if len(s) == 26:
        print('None')

else:
    for i in s:
        d.remove(i)
    print(d[0])

Submission status: Accepted

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

Submission status: Accepted

Solution code:
alpha = [chr(ord('a') + i) for i in range(26)]
n = list(input())
is_not_exist = True
for i in alpha:
    if i not in n:
        print(i)
        is_not_exist = False
        break
if is_not_exist:
    print(None)

Submission status: Accepted

Solution code:
import sys
# A,B,C = [int(n) for n in input().split()]
# N = int(input())
# A = [0]*N
# for i in range(N):
#     A[i] = int(input())
S = str(input())
ll = list("abcdefghijklmnopqrstuvwxyz")
for al in ll:
    if not (al in S):
        print(al)
        sys.exit()
print("None")

Submission status: Accepted

Solution code:
s = input()
s_set = set(list(s))
alphabet = [chr(i) for i in range(97,97+26)]#int to alphabet
#Alphabet = [chi(i) for i in range(65,65+26)]
alphabet_set = set(alphabet)
nokori = alphabet_set - s_set
nokori_sort = sorted(list(nokori))
if len(nokori_sort) == 0:
	print("None")
	exit()
print(nokori_sort[0])

Submission status: Accepted

Solution code:
s=input()
s=set(s)
t=[ord(i) for i in s]
t.sort()
#print(t)
flag=0

for i in range(97,122+1):
  if t.count(i)==0 and flag==0:
    ans=i
    flag=1

print(chr(ans) if flag==1 else 'None')

Submission status: Accepted

Solution code:
import string


S = list(input())
F = False

for s in list(string.ascii_lowercase):
    if s in S:
        continue
    else:
        print(s)
        F = True
        break

if F == False:
    print('None')

Submission status: Accepted

Solution code:
# ABC 071
def db(x): 
    global debug
    if debug: print(x)
debug = False
S = input()
alpha = [chr(ord('a')+i) for i in range(26)]
for c in S: 
    if c in alpha: alpha.remove(c)
db(alpha)
if alpha==[]: ans = 'None'
else: ans = alpha[0]
print(ans)

Submission status: Accepted

Solution code:
S = input()
chrs = [0]*26
for i in S:
    chrs[ord(i)-97]+=1
ans = 'None'
for index,i in enumerate(chrs):
    if(i==0):
        ans=chr(index+97)
        break
print(ans)

Submission status: Accepted

Solution code:
# word = [w for w in input()]
word = input()
alpha_lists = [-1] * 26
flg = True

for w in word:
  alpha_lists[ord(w) - ord('a')] = 1

for a in range(len(alpha_lists)):
  if(alpha_lists[a] == -1):
    print(chr(ord('a') + a))
    flg = False
    break
    
if(flg):
  print("None")

Submission status: Accepted

Solution code:
import string

S = input()

for alp in string.ascii_lowercase:
    if alp not in S:
        print(alp)
        exit()

print("None")

Submission status: Accepted

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

Submission status: Accepted

Solution code:
S = sorted(set(input()))
dic = 'abcdefghijklmnopqrstuvwxyz'
for c in S:
    if c in dic:
        dic = dic.replace(c, '')
if len(dic) != 0:
    print(dic[0])
else:
    print('None')

Submission status: Accepted

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

Submission status: Accepted

Solution code:
S = input()
alpha = list("abcdefghijklmnopqrstuvwxyz")
for s in S:
    if s in alpha:
        alpha.remove(s)
if len(alpha)>0:
    print(alpha[0])
else:
    print("None")

Submission status: Accepted

Solution code:
# _*_ coding:utf-8 _*_
#  Atcoder_Beginners_Contest071-B
#  TODO https://atcoder.jp/contests/abc071/tasks/abc071_b

def  firstCharNotFound(givenString):
	# initialize for char
	checkList = [False for _ in range(0,26,+1)]
	stringLength = range(0,len(givenString),+1)
	for pos in stringLength:
		charIntVersion = ord(givenString[pos])
		checkList[charIntVersion-97]=True
	charRange = range(0,26,+1)
	firstPosition = -1
	for pos in charRange:
		if checkList[pos]==False:
			firstPosition = pos
			break
	if firstPosition == -1:
		return "None"
	else :
		return chr(firstPosition+97)

if __name__ == '__main__':
	S = input().strip()
	solution=firstCharNotFound(S)
	print("{}".format(solution))

Submission status: Accepted

Solution code:
print(min(set(map(chr,range(97,123)))-set(input())or["None"]))
#コピペです。

Submission status: Accepted

Solution code:
s=list(input())
s.sort()
l=[chr(ord("a")+i) for i in range(26)]
n=[]
for j in l:
  if j not in s:
    n.append(j)
n.sort()
if len(n)==0:
  print("None")
else:
  print(n[0])

Submission status: Accepted

Solution code:
s=input()
s1=list(s)
s2=set(s1)
az="abcdefghijklmnopqrstuvwxyz"
az1=list(az)
az2=set(az1)
ans=az2-s2
ans1=list(ans)
ans1.sort()
if len(ans1)!=0:
    print(ans1[0])
else:
    print("None")

Submission status: Accepted

Solution code:
s = input()
ans = 'a'
for i in range(26):
    if ans not in s:
        print(ans)
        exit()
    ans = chr(ord(ans) + 1)
print("None")

Submission status: Accepted

Solution code:
import sys


def input():
    return sys.stdin.readline()[:-1]


def ii(t: type = int):
    return t(input())


def il(t: type = int):
    return list(map(t, input().split()))


def iml(N: int, t: type = int):
    return [t(input()) for _ in range(N)]


S = sorted(set(ii(str)))
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())
ans='A'
for i in range(26):
    if chr(ord('z')-i) not in S:
        ans=chr(ord('z')-i)
if ans=='A':
    print('None')
else:
    print(ans)

Submission status: Accepted

Solution code:
S = input()
dic = [chr(i) for i in range(ord('a'), ord('z')+1)]
flag = True
for j in range(len(dic)):
    if dic[j] not in S:
        print(dic[j])
        flag = False
        break
if flag:
    print('None')

Submission status: Accepted

Solution code:
import sys

input_ = [ord(_) for _ in sys.stdin.readlines()[0].strip()]
alphabets = [i + 96 for i in range(1, 27)]
for c in input_:
  if c in alphabets:
    alphabets.remove(c)

res = sorted(alphabets)
if len(res) > 0:
  print(chr(res[0]))
else:
  print('None')

Submission status: Accepted

Solution code:
s = list(input())
count=0
for i in range(97, 123):
    if(chr(i) not in s):
        print(chr(i))
        count+=1
        break
if(count==0):
    print("None")

Submission status: Accepted

Solution code:
s = str(input())
s = sorted(s)
d = [0] * 150
for i in range(len(s)):
    d[ord(s[i])] += 1
for i in range(97,122+1):
    if d[i] == 0:
        print(chr(i))
        break
    if i == 122:
        print("None")

Submission status: Accepted

Solution code:
def abc071_b():
    s = input()
    alpha = [chr(i) for i in range(ord("a"), ord("z") + 1)]
    for char in set(s):
        alpha.remove(char)

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


abc071_b()

Submission status: Accepted

Solution code:
s=input()
tmp="abcdefghijklmnopqrstuvwxyz"
if len(set(s))==26:
    print("None")
    exit()
for i in tmp:
    if not i in s:
        print(i)
        break

Submission status: Accepted

Solution code:
import string
pp = list(input())
pp=list(set(pp))
pp.sort()
pp.append("1")
s = ""
x = list(string.ascii_lowercase)
x.append("None")
for j in range(len(pp)):
    if pp[j] != x[j]: 
        s = x[j]
        break
    elif pp[j] =="1":
        s = "None"
print(s)

Submission status: Accepted

Solution code:
S = sorted(set(input()))
dic = "abcdefghijklmnopqrstuvwxyz"
for s in S:
  if(s in dic):
    dic = dic.replace(s,'')
if(dic != ''):
  print(dic[0])
else:
  print("None")

Submission status: Accepted

Solution code:
S = sorted(input())
dic = "abcdefghijklmnopqrstuvwxyz"
for s in S:
  if(s in dic):
    dic = dic.replace(s,'')
if(dic != ''):
  print(dic[0])
else:
  print("None")

Submission status: Accepted

Solution code:
S = input()

s_set = set()
for s in S:
    s_set.add(s)

ans = ""
for temp in range(26):
    temp_s = chr(ord("a") + temp)
    if not temp_s in s_set:
        ans = temp_s
        break
else:
    ans = "None"

print(ans)

Submission status: Accepted

Solution code:
s = input()
res = "None"
for i in "abcdefghijklmnopqrstuvwxyz":
    if s.count(i) <= 0:
        res = i
        break
print(res)

Submission status: Accepted

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

Submission status: Accepted

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


def main():
    """Function."""
    s = str(input())

    alpha = ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k",
             "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v",
             "w", "x", "y", "z"]
    base = set()
    for dum in alpha:
        base.add(dum)

    check = set()
    for i in range(len(s)):
        check.add(s[i])

    dum = base - check

    if dum == set():
        print("None")
    else:
        print(min(list(dum)))


if __name__ == "__main__":
    main()

Submission status: Accepted

Solution code:
S = list(input())
S = set(S)
alpha = [chr(ord('a') + i) for i in range(26)]
alpha = set(alpha)
anset = alpha - S
anset = sorted(list(anset))

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

Submission status: Accepted

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


if __name__ == '__main__':
    main()

Submission status: Accepted

Solution code:
s = input()
d = {}
for c in "abcdefghijklmnopqrstuvwxyz":
    d[c] = 0

for c in s:
    d[c] += 1

result = None
for k, v in sorted(d.items(), key=lambda x: x[0]):
    if v == 0:
        result = k

        break

print(result if result else "None")

Submission status: Accepted

Solution code:
s = input()
alpha = [True for _ in range(26)]
for _s in s:
    alpha[ord(_s) - ord("a")] = False
for i in range(len(alpha)):
    if alpha[i]:
        print(chr(i + ord("a")))
        exit()
print("None")

Submission status: Accepted

Solution code:
S = input()
for c in 'abcdefghijklmnopqrstuvwxyz':
    if c not in S:
        print(c)
        exit()
print('None')

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:
s = input()
a = "None"
list = "abcdefghijklmnopqrstuvwxyz"
for i in list:
    if i not in s:
        a = i
        break
        
print(a)

Submission status: Accepted

Solution code:
S = input()
msg = "None"
for i in range(26) :
    c = chr(ord("a")+i)
    if(S.find(c) == -1) :
        msg = c
        break

print(msg)

Submission status: Accepted

Solution code:
S = input()
T = 'abcdefghijklmnopqrstuvwxyz'
diff = sorted(list(set(T) - set(S)))
if diff:
    print(diff[0])
else:
    print('None')

Submission status: Accepted

Solution code:
from collections import Counter

S = input()

cs = Counter(S)

result = "None"

for i in range(26):
    c = chr(ord("a") + i)
    if c not in cs:
        result = c
        break

print(result)

Submission status: Accepted

Solution code:
# coding: utf-8
S = set(input())
ans = "None"
for s in "abcdefghijklmnopqrstuvwxyz":
    if s not in S:
        ans = s
        break
print(ans)

Submission status: Accepted

Solution code:
# coding: utf-8
al = "abcdefghijklmnopqrstuvwxyz"
S = set(input())
for s in al:
    if len(al) == len(S):
        print("None")
        break
    elif s not in S:
        print(s)
        break

Submission status: Accepted

Solution code:
s=input()
ch='abcdefghijklmnopqrstuvwxyz'

s=set(s)
ch=set(ch)
s=ch-s
s=sorted(s)

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

Submission status: Accepted

Solution code:
def not_found_minchar(S):
    for o in range(ord('a'), ord('z') + 1):
        if chr(o) not in S:
            return chr(o)
    return "None"

S = raw_input()
print not_found_minchar(S)

Submission status: Accepted

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

Submission status: Accepted

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

Submission status: Accepted

Solution code:
s = input()
check = 'abcdefghijklmnopqrstuvwxyz'

s = set(s)
check = set(check)
s = check - s
s = sorted(s)
if(s):
    print(s[0])
else:
    print('None')

Submission status: Accepted

Solution code:
S = input()
for c in 'abcdefghijklmnopqrstuvwxyz':
    if not c in S:
        print(c)
        exit()
print('None')

Submission status: Accepted

Solution code:
s = input()
count = 0
al = "qwertyuiopasdfghjklzxcvbnm"
al_list = [i for i in al]
al_list.sort()
for i in al_list:
    if i not in s:
        print(i)
        break
    else:
        count += 1
if count == len(al_list):
    print("None")

Submission status: Accepted

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

s.sort()

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

Submission status: Accepted

Solution code:
s = input()
dup = set(s)
ans = ''

if   len(dup) == 26:
    print('None')
    exit()
else:
    chrs = sorted(dup)
    for i in range(97,123):
        if chr(i) not in chrs:
            ans = chr(i)
            break
print(ans)

Submission status: Accepted

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

Submission status: Accepted

Solution code:
import collections
s = input()
alpha = [chr(i) for i in range(ord('a'), ord('z')+1)]
c = collections.Counter(s)
for al in alpha:
    if al not in c:
        print(al)
        exit()
print("None")

Submission status: Accepted

Solution code:
s = input()
alfs = 'abcdefghijklmnopqrstuvwxyz'

for alf in alfs:
    if alf in s:
        continue
    else:
        print(alf)
        exit()
print('None')

Submission status: Accepted

Solution code:
S=set(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"]
ans=0
for i in Al:
    if i not in S:
        print(i)
        exit()
print('None')

Submission status: Accepted

Solution code:
S = { i for i in input() }
for c in "abcdefghijklmnopqrstuvwxyz":
    if not c in S:
        print(c)
        break
else:
    print("None")

Submission status: Accepted

Solution code:
flag=False
s=input()
for i in "abcdefghijklmnopqrstuvwxyz":
    if i in s:
        continue
    else:
        print(i)
        flag=True
        break
if flag==False:
    print("None")

Submission status: Accepted

Solution code:
s = input()

set_s = set(s)

abc = 'abcdefghijklmnopqrstuvwxyz'

if len(abc) != 26:
	print('err')

set_abc = set(abc)

set_abc -= set_s

ans =[]

for c in set_abc:
	ans.append(c)
	
ans.sort()

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

Submission status: Accepted

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

Submission status: Accepted

Solution code:
S = input()
S = set(S)
alp = [chr(ord('a') + i) for i in range(26)]
for i in alp:
  if i not in S:
    print(i)
    break
else:
  print("None")

Submission status: Accepted

Solution code:
import sys
sin={'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())
snum=len(list(set(s)))
if snum==26:
    print('None')
    sys.exit(0)

kotae=list(sin-set(s))
kotae.sort()
print(kotae[0])

Submission status: Accepted

Solution code:
a = "abcdefghijklmnopqrstuvwxyz"
b = input()
count = 0
for i in range(26):
    if a[i] not in b:
        print(a[i])
        count += 1
        break
if count == 0:
    print("None")

Submission status: Accepted

Solution code:
S = input()
N = len(S)
for i in range(26):
    flag = True
    for j in range(N):
        if S[j] == chr(i + ord("a")):
            flag = False

    if flag:
        print(chr(i + ord("a")))
        exit()

print("None")

Submission status: Accepted

Solution code:
a = list(input())
b = "abcdefghijklmnopqrstuvwxyz"
c = list(b)

for i in range(len(c)):
  if c[i] not in a:
    print(c[i])
    break
  else:
    continue
else:
  print("None")

Submission status: Accepted

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

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

print('None')

Submission status: Accepted

Solution code:
s = input()
alphabet = 'abcdefghijklmnopqrstuvwxyz'
li = list(alphabet)

for item in li:
    if s.find(item) == -1:
        print(item)
        break
else:
    print('None')

Submission status: Accepted

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

s=input()
l=string.ascii_lowercase
for i in l:
    if i not in s:
        print(i)
        break
else:
    print('None')

Submission status: Accepted

Solution code:
S = list(input().rstrip())
ts = 'abcdefghijklmnopqrstuvwxyz'

ns = []

for c in S:
    if c not in ns:
        ns.append(c)


if len(ns) == 26:
    print('None')
else:
    ns.sort()
    for tc in ts:
        if tc not in ns:
            print(tc)
            break

Submission status: Accepted

Solution code:
j = set('abcdefghijklmnopqrstuvwxyz')
s = set(input())
k = sorted(j - s)

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

Submission status: Accepted

Solution code:
x = set('abcdefghijklmnopqrstuvwxyz')
s = set(input())
y = sorted(x - s)

if y:
  print(y[0])
else:
  print('None')

Submission status: Accepted

Solution code:
s = input()
chk = "abcdefghijklmnopqrstuvwxyz"
ans = ""
for i in range(len(chk)):
    if chk[i] not in s:
        ans = chk[i]
        break
print(ans if ans != "" else "None")

Submission status: Accepted

Solution code:
alphabet = map(chr, range(ord("a"), ord("z") + 1))
alphabet = set(list(alphabet))
s = input()
s = set(list(s))
try:
    print(min(alphabet - s))
except:
    print("None")

Submission status: Accepted

Solution code:
S = list(input())
set(S)
A = "abcdefghijklmnopqrstuvwxyz"
list(A)
count = 0
ans = "None"
an = -1
for i in range(len(A)):
    for j in range(len(S)):
        if A[i] == S[j]:
            count = 1
    else:
        if count == 1:
            count = 0
        elif count == 0:
            an = i
            break
if an != -1:
    print(A[an])
else:
    print("None")

Submission status: Accepted

Solution code:
s = input()

al = "abcdefghijklmnopqrstuvwxyz"
num = len(al)

for i in range(num):
	if al[i] not in s:
		print(al[i])
		break
else:
	print("None")

Submission status: Accepted

Solution code:
S = input()
l = [True]*26

for i in S:
    l[ord(i)-ord("a")] = False

for i in range(26):
    if(l[i] == True):
        print(chr(ord("a")+i))
        break
else:
    print("None")

Submission status: Accepted

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

Submission status: Accepted

Solution code:
import string
s=set(input())
d=set(string.ascii_lowercase)
print('None' if len(s)==26 else sorted(list(d-s))[0])