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(list(input()))
A='abcdefghjiklmnopqrstuvwxyz'
for i in A:
  if i not in S:
    print(i)
    break
else:
  print('None')

Submission status: Accepted

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

Submission status: Accepted

Solution code:
s=set(input())

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

ans = sorted(list(apl-s))
print(ans[0] if len(apl-s)!=0 else 'None')

Submission status: Accepted

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

Submission status: Accepted

Solution code:
s = input()
alphabet = "abcdefghijklmnopqrstuvwxyz"
for chr in alphabet:
  if chr not in s:
    print(chr)
    break
else:
  print("None")

Submission status: Accepted

Solution code:
S = input()

import string

S = list(sorted(S))
T = string.ascii_lowercase

for t in T:
    if t not in S:
        print(t)
        break
        
else:
    print("None")

Submission status: Accepted

Solution code:
from string import ascii_lowercase as a
s = set(input())
for c in a:
    if c not in s:
        print(c)
        break
else:
    print('None')

Submission status: Accepted

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

def main():
    S = input().strip()
    ch = "abcdefghijklmnopqrstuvwxyz"
    check = [False] * len(ch)
    for c in S:
        for i in range(len(ch)):
            if c == ch[i]:
                check[i] = True
    
    ans = "None"
    for i in range(len(ch)):
        if not check[i]:
            ans = ch[i]
            break
    print(ans)


if __name__ == "__main__":
    main()

Submission status: Accepted

Solution code:
S = set(map(str, (input())))
s = list(S)
s.sort()
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']
for i in range(len(s)):
    alphabet.remove(s[i])

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

Submission status: Accepted

Solution code:
S = set(input())
import string
letters=string.ascii_lowercase
S^=set(letters)
if len(S) == 0:
    print('None')
else:
    print(sorted(S)[0])

Submission status: Accepted

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

Submission status: Accepted

Solution code:
s=input()
for i in ['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 (i in s)!=True:
        print(i)
        exit()
print('None')

Submission status: Accepted

Solution code:
import sys
s = sorted(input())
a = ord('a')
for j in range(26):
    b = a
    for i in s:
        if a == ord(i):
            a += 1
            break
    if a == b:
        print(chr(a))
        sys.exit()
print('None')

Submission status: Accepted

Solution code:
l=set(map(chr,range(97,123)))
ans = sorted(l ^ set(input()))
print('None' if len(ans)==0 else ans[0])

Submission status: Accepted

Solution code:
S = sorted(set([i for i in input()]))
for i in "abcdefghijklmnopqrstuvwxyz":
    if i not in S:
        print(i)
        break
else:print("None")

Submission status: Accepted

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

Submission status: Accepted

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

Submission status: Accepted

Solution code:
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']
s = set(input())
for i in a:
    if i not in s:
        print(i)
        break
else:
    print('None')

Submission status: Accepted

Solution code:
arr = [s for s in input()]
alphabet = [s for s in 'abcdefghijklmnopqrstuvwxyz']

arr = sorted(list(set(arr)))

for i in range(len(alphabet)):
  if arr.count(alphabet[i]) == 0:
    print(alphabet[i])
    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))
        exit()
print('None')

Submission status: Accepted

Solution code:
from string import*
s =input()
s=sorted(s)
alpha_l =[ascii_lowercase[i] for i in range(0,26)]
n='a'
for x in range(0,26):
	if x == 25 and alpha_l[x] in s:
		n = 'None'
	elif alpha_l[x] in s:
		continue
	else:
		n = alpha_l[x]
		break
print(n)

Submission status: Accepted

Solution code:
import sys
import copy
import  math
import bisect
from collections import *
from operator import itemgetter
"""
from fractions import gcd
def lcm(x, y):
    return (x * y) // gcd(x, y)
"""
stdin = sys.stdin
ni = lambda: int(ns())
na = lambda: list(map(int, stdin.readline().split()))
ns = lambda: stdin.readline()

s = input()
li = [chr(ord('a') + i) for i in range(26)]
for c in s:
    if c in li:
        li.remove(c)
if li:
    print(li[0])
else:
    print('None')

Submission status: Accepted

Solution code:
import string

S = set(list(input()))

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

print('None')

Submission status: Accepted

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

for i in abc:
    if s == abc:
        print('None')
        break
    elif i not in s:
        print(i)
        break

Submission status: Accepted

Solution code:
# ABC071b
import sys
input = sys.stdin.readline
sys.setrecursionlimit(10**6)

alphabet = 'abcdefghijklmnopqrstuvwxyz'

s = input()
for i in s:
    # print(i)
    alphabet = alphabet.replace(i, '')
print(alphabet[0] if len(alphabet) > 0 else 'None')

Submission status: Accepted

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

Submission status: Accepted

Solution code:
d=[0]*26
for i in input():
    d[ord(i)-97]+=1
print(chr(97+d.index(0)) if 0 in d else"None")

Submission status: Accepted

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

Submission status: Accepted

Solution code:
import string
s = input()

s = sorted(set(s))
moji = [chr(i) for i in range(ord('a'), ord('z')+1)]
# print(s)
# print(moji)

def b():
    for i in range(len(moji)):
        if i > len(s)-1 or moji[i] != s[i]:
            return moji[i]
    return "None"

print(b())

Submission status: Accepted

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

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:
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']
L = [0 for i in range(26)]
S = input()
for s in S:
  L[ABC.index(s)]+=1
f = True
for i in range(26):
  if L[i] == 0:
    f = False
    print(ABC[i])
    break
if f:
  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:
S=list(input())
all=['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 all:
  if s not in S:
    print(s)
    exit()
print('None')

Submission status: Accepted

Solution code:
import string
S = input()
al = string.ascii_lowercase
for x in al:
    if x not in S:
        print(x)
        break
else:
    print("None")

Submission status: Accepted

Solution code:
s = input()
s_num = [ord(s[i]) for i in range(len(s))]
s_num = set(sorted(list(s_num)))

for i in range(ord('a'), ord('z')+2):
  if i == ord('z')+1:
    print('None')
  elif i not in s_num:
    print(chr(i))
    break

Submission status: Accepted

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

Submission status: Accepted

Solution code:
S = input()

T = list('abcdefghijklmnopqrstuvwxyz')

for s in S:
    if s in T:
        T.remove(s)
if not T:
    print('None')
else:
    print(T[0])

Submission status: Accepted

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

Submission status: Accepted

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

Submission status: Accepted

Solution code:
L = "".join([chr(i) for i in range(97, 97 + 26)])
for i in set(list(input())):
    L = L.replace(i, "")
if L == "":
    print("None")
else:
    print(L[0])

Submission status: Accepted

Solution code:
L = "".join([chr(i) for i in range(97, 97 + 26)])
for i in list(input()):
    L = L.replace(i, "")
if L == "":
    print("None")
else:
    print(L[0])

Submission status: Accepted

Solution code:
s = set(input())
alpha = "abcdefghijklmnopqrstuvwxyz"
f = False
ans = ""
for i in alpha:
    if not i in s:
        f = True
        ans = i
        break
if f:
    print(ans)
else:
    print("None")

Submission status: Accepted

Solution code:
alp = ["a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"]
s = input()
s = set(s)
if len(s)==len(alp):
    print("None")
else:
    s = sorted(s)
    s = list(s)
    for i in alp:
        if i not in s:
          print(i)
          break

Submission status: Accepted

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

import string

S = input()

set_s = set(S)
for c in string.ascii_lowercase:
    if c not in set_s:
        print(c)
        exit()
else:
    print('None')

Submission status: Accepted

Solution code:
def main():
    sc = set(list(input()))
    for c in "abcdefghijklmnopqrstuvwxyz":
        if c not in sc:
            return c
    return "None"



if __name__ == '__main__':
    print(main())

Submission status: Accepted

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

Submission status: Accepted

Solution code:
s = sorted(list(set(input())))
lst = 'abcdefghijklmnopqrstuvwxyz'
flag = False
for i in lst:
    if i not in s:
        flag = True
        print(i)
        break
if flag == False:
    print('None')

Submission status: Accepted

Solution code:
import sys
s = sys.stdin.readline().rstrip()
num = [0 for i in range(ord("z")-ord("a")+1)] #バケット(a-z)
for i in range(len(s)):
    num[ord(s[i])-ord("a")] += 1
for i in range(26):
    if num[i] == 0:
        print(chr(i+ord("a")))
        break
else:
    print("None")

Submission status: Accepted

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

s = sorted(list(set(list(input()))))
# print(s)

for c in list("abcdefghijklmnopqrstuvwxyz"):
    if c in s:
        pass
    else:
        print(c)
        exit(0)

print("None")

Submission status: Accepted

Solution code:
S=input()
alphabet=[chr(x) for x in range(ord("a"),ord("z")+1)]
A={x: 0 for x in alphabet}
for s in S:
    A[s]+=1
for c in alphabet:
    if A[c]==0:
        print(c)
        exit()
else:
    print("None")

Submission status: Accepted

Solution code:
s=list(input())
t=[ord(si) for si in s]
for i in range(97,124):
  if i==123:
    print('None')
    break
  if not i in t:
    print(chr(i))
    break

Submission status: Accepted

Solution code:
al = list("abcdefghijklmnopqrstuvwxyz")
S = list(set(list(input())))
S.sort()
for i in S:
  al.remove(i)

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

Submission status: Accepted

Solution code:
s = input()
sset = set(s)
slist = list(sset)
slist.sort()
char = "abcdefghijklmnopqrstuvwxyz"
flg = False

for i in range(26):
  if len(slist) <= i:
    print(char[i])
    flg = True
    break
  if slist[i] != char[i]:
    print(char[i])
    flg = True
    break

  
if flg == False:
  print("None")

Submission status: Accepted

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

Submission status: Accepted

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

Submission status: Accepted

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

Submission status: Accepted

Solution code:
s = set(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 = input()
ans = 'None'

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 i in range(len(a)):
	if s.find(a[i]) == -1:
		ans = a[i]
		break
	
print(ans)

Submission status: Accepted

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

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

if s==a:
    print('None')
for i in a:
    if i not in s:
        print(i)
        break

Submission status: Accepted

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

for i in range(len(l)):
    if l[i] not in s:
        print(l[i])
        exit()
print('None')

Submission status: Accepted

Solution code:
S = input()

ret = [0] * 26
for s in S :
    ret[ord(s)-97] = 1
    
for i in range(26) :
    if ret[i] == 0 :
        print(chr(i+97))
        break
else :
    print('None')

Submission status: Accepted

Solution code:
alphabets = list("abcdefghijklmnopqrstuvwxyz")
appeared = []
S = input()
for c in S:
    if not c in appeared:
        appeared.append(c)
for i in alphabets:
    if not i in appeared:
        print(i)
        exit()
print("None")

Submission status: Accepted

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

Submission status: Accepted

Solution code:
S = input()

A = [0 for _ in range(26)]

for s in S:
    A[ord(s) - ord('a')] += 1

for i, a in enumerate(A):
    if a == 0:
        print(chr(i + ord('a')))
        break
else:
    print("None")

Submission status: Accepted

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

def main(S):
    A = list("abcdefghijklmnopqrstuvwxyz")
    for i in S:
        if i in A:
            A.pop(A.index(i))

    print(A[0]) if A else print("None")
    
if __name__ == '__main__':
    S = input()
    main(S)

Submission status: Accepted

Solution code:

S = input()
for i in range(ord('a'), ord('z')+1):
    c = chr(i)
    if not c in S:
        print(c)
        exit()

print('None')

Submission status: Accepted

Solution code:
s = list(input())
abc = list('abcdefghijklmnopqrstuvwxyz')
not_abc = []
cnt = 0

for i in abc:
  if i not in s:
    not_abc.append(i)
    cnt = cnt + 1
  
if cnt == 0:
  print('None')
  
elif cnt >= 1:
  print(sorted(not_abc)[0])

Submission status: Accepted

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

Submission status: Accepted

Solution code:
def find_missing(s):
  letters = set(s)
  for i in range(ord('a'), ord('z') + 1):
    if chr(i) not in letters:
      return chr(i)
    
print(find_missing(input()))

Submission status: Accepted

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

Submission status: Accepted

Solution code:
s=list(input())
s=set(s)
alp="abcdefghijklmnopqrstuvwxyz"
def search():
  for a in alp:
    if not a in s:
      print(a)
      return
  print("None")
  return

search()

Submission status: Accepted

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

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

Submission status: Accepted

Solution code:
alp=[chr(i) for i in range(97, 97+26)]
#文字コードで並び替える
#それぞれ一つずつにする
#print(alp)
s=sorted(set(list(input())))

for i in range(len(s)):
    if s[i]!=alp[i]:
        print(alp[i])
        break
    if i==len(s)-1:
        if len(s) != len(alp):
            print(alp[i+1])
        else:
            print("None")

Submission status: Accepted

Solution code:
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"]
s = input()
s = list(s[i] for i in range(len(s)))
for x in X:
  if x not in s:
    print(x)
    break
else:
  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
else:
  print("None")

Submission status: Accepted

Solution code:
# input 
S = input()

# processing
cand = set('abcdefghijklmnopqrstuvwxyz') - set(S)
if cand:
    res = min(cand)
else:
    res = 'None'

# output    
print(res)

Submission status: Accepted

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

Submission status: Accepted

Solution code:
strings = list(input())
alfabet  = 'abcdefghijklmnopqrstuvwxyz'

for i in alfabet:
    if strings.count(i) == 0:
        result = i
        break
else:
    result = "None"

print(result)

Submission status: Accepted

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

Submission status: Accepted

Solution code:
s = set(list(input()))
alf = [chr(i) for i in range(97, 97+26)]
count = 0

for a in alf:
    if a not in s:
        print(a)
        count += 1
        exit()

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

Submission status: Accepted

Solution code:
s = list(input())
alphabet = list('abcdefghijklmnopqrstuvwxyz')
ans_list = list(set(alphabet)-set(s))
if ans_list:
    ans_list.sort()
    print(ans_list[0])
else:
    print('None')

Submission status: Accepted

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

Submission status: Accepted

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

Submission status: Accepted

Solution code:
S = input()

for i in range(ord('a'), ord('z')+1):
    if chr(i) not in list(S):
        print(chr(i))
        exit()

print('None')

Submission status: Accepted

Solution code:
import collections
s = collections.Counter(input()).keys()
d = list("abcdefghijklmnopqrstuvwxyz")
for i in d:
    if i not in s:
        print(i)
        exit()
print("None")

Submission status: Accepted

Solution code:
sl=list(input())
al="abcdefghijklmnopqrstuvwxyz"
l=list(al)
mydic={}
for st in l :
  mydic[st]=0 

for st in sl :
  mydic[st]=mydic[st]+1
ans=[]

for key in mydic.keys() :
  if mydic[key] ==0 :
    ans.append(key)
ans.sort()
if len(ans)==0 :
  print("None")
else :
  print(ans[0])

Submission status: Accepted

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

s=input()
for x in alpha:
    if x not in s:
        print(x)
        exit()
    
print("None")

Submission status: Accepted

Solution code:
S = input()

alphabets = list("abcdefghijklmnopqrstuvwxyz")

ans = "None"

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

print(ans)

Submission status: Accepted

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

Submission status: Accepted

Solution code:
s = input()
ans = set(map(chr,range(ord('a'),ord('z')+1))) - set(s)
print(min(ans) if len(ans)!=0 else 'None')

Submission status: Accepted

Solution code:
s = input()

ascii_lowercase = 'abcdefghijklmnopqrstuvwxyz'
for c in ascii_lowercase:
    if s.count(c) == 0:
        print(c)
        exit()
print('None')

Submission status: Accepted

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

Submission status: Accepted

Solution code:
S = input()
alphabet = 'abcdefghijklmnopqrstuvwxyz'
for s in S:
    alphabet = alphabet.replace(s, '')
if not alphabet:
    print('None')
else:
    print(alphabet[0])

Submission status: Accepted

Solution code:

nlist = [None] * 150

def main():
    
    stri = input()
    
    for i in range(len(stri)):
        ind = ord(stri[i])
        nlist[ind] = 1
    
    for i in range(len(nlist)):
        if nlist[i] == None and (i > 96 and i<123) :
            print(str(chr(i)))
            return
    print("None")

if __name__== "__main__" : main()

Submission status: Accepted

Solution code:
S = list(input())
abc = list("abcdefghijklmnopqrstuvwxyz")
table = []
for s in abc:
  if s not in S:
    table.append(s)
table.sort()
print(table[0] if len(table) > 0 else "None")

Submission status: Accepted

Solution code:
ANS = sorted({chr(i) for i in range(97, 123)} - set(input()))
print(ANS[0] if ANS else 'None')

Submission status: Accepted

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

s = input().strip()
a = [c for c in "abcdefghijklmnopqrstuvwxyz"]
for c in s:
    if c in a:
        a.remove(c)
if len(a) == 0:
    print("None")
else:
    print(a[0])

Submission status: Accepted

Solution code:
S = input()

li = [chr(i) for i in range(ord("a"), ord("z") + 1)]

for i in range(len(S)):
  if S[i] in li:
    li.remove(S[i])
print (li[0] if len(li) != 0 else "None")

Submission status: Accepted

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

Submission status: Accepted

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

Submission status: Accepted

Solution code:
S = input()
S = sorted(S)
i = 0
if S[0] != "a":
    print("a")
    exit(0)
while i<len(S)-1:
    if ord(S[i]) == ord(S[i+1]) or ord(S[i]) == ord(S[i+1])-1:
        i += 1
    else:
        print(chr(ord(S[i])+1))
        exit(0)

if S[-1] == "z":
    print("None")
else:
    print(chr(ord(S[i])+1))

Submission status: Accepted

Solution code:
import sys
s=input()
l="abcdefghijklmnopqrstuvwxyz"
for i in range(len(l)): #aから順に調べていく
    if l[i] in s: #もし文字列sの中にa..があればそれを表示
        continue
    else:
        print(l[i])
        sys.exit()
print("None")

Submission status: Accepted

Solution code:
S = list(input())
B = list('abcdefghijklmnopqrstuvwxyz')
D = {}
tmp = 0
for i in range(len(B)):
    D[B[i]] = 0
for i in S:
    D[i] += 1
for i in B:
    if D[i] == 0:
        print(i)
        break
else:
    print('None')

Submission status: Accepted

Solution code:
from string import ascii_lowercase
s = input()

d = set([s[i] for i in range(len(s))])
ans = "None"
for c in ascii_lowercase:
    if c not in d:
        ans = c
        break

print(ans)

Submission status: Accepted

Solution code:
S = input()
alpha = [chr(ord('a') + i) for i in range(26)]
n=0
c=-1
while c == -1 and n < 26:
  if not alpha[n] in S:
    c = n
    break
  n+=1
if c == -1:
  print('None')
else:
  print(alpha[n])

Submission status: Accepted

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

Submission status: Accepted

Solution code:
import string
S = input()
for s in string.ascii_lowercase:
    if s not in S:
        print(s)
        break
else:
    print('None')

Submission status: Accepted

Solution code:
s = input()
t = set()
for i in range(len(s)):
  t.add(s[i])
o = list(t)
o.sort()
u = 'qwertyuiopasdfghjklzxcvbnm'
v = []
for i in range(len(u)):
  v.append(u[i])
v.sort()
now = 0
if len(o) == 26:
  print('None')
else:
  for i in range(26):
    if i >= len(t):
      print(v[i])
      break
    elif o[i] == v[i]:
      now += 1
    else:
      print(v[now])
      break

Submission status: Accepted

Solution code:
str = input()
n = [0 for i in range(26)]

for j in range(len(str)):
    for i in range(26):
        if ord(str[j]) == ord('a')+i: n[i] += 1

check_flag = 0
for i in range(26):
    if check_flag==0 and n[i] == 0:
        check_flag = 1
        print(chr(97+i))
        break

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

Submission status: Accepted

Solution code:
s = input()
ls = ["a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"]
c = 0
for i in ls:
  if i in s:
    c += 1
  else:
    print(i)
    break
    
if c >= 26:
  print("None")

Submission status: Accepted

Solution code:
ans = sorted({chr(i) for i in range(97, 123)} - set(input()))
print(ans[0] if ans else 'None')

Submission status: Accepted

Solution code:
import itertools
s = input()
cnt = ord('a')
for k, _ in itertools.groupby(sorted(s)):
  if not cnt == ord(k):
    break
  cnt += 1
print([chr(cnt), 'None'][cnt>ord('z')])

Submission status: Accepted

Solution code:
text = input()
alphabet = 'abcdefghijklmnopqrstuvwxyz'

for s in text:
    alphabet = alphabet.replace(s, '')

if alphabet is '':
    print('None')
else:
    print(alphabet[0])

Submission status: Accepted

Solution code:
diff = set(chr(ord("a") + i) for i in range(26)) - set(input().rstrip("\n"))

print((list(sorted(diff))+["None"])[0])

Submission status: Accepted

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


S = list(input())

alphabets = list('abcdefghijklmnopqrstuvwxyz')
for alphabet in alphabets:
    if alphabet in S:
        continue
    else:
        print(alphabet)
        sys.exit()

print('None')

Submission status: Accepted

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

Submission status: Accepted

Solution code:
s = input()
abc = {"a":0,"b":0,"c":0,"d":0,"e":0,"f":0,"g":0,"h":0,"i":0,"j":0,"k":0,"l":0,"m":0,"n":0,"o":0,"p":0,"q":0,"r":0,"s":0,"t":0,"u":0,"v":0,"w":0,"x":0,"y":0,"z":0}
for i in range(len(s)):
    abc[s[i]]+=1
alle = True
for i in abc:
    if abc[i] == 0:
        print(i)
        alle = False
        break
if alle:
    print("None")

Submission status: Accepted

Solution code:
s = list(input())

s_sorted = sorted(set(s))
alpha_dict = {chr(a):0 for a in range(ord('a'), ord('z')+1)}
#{'a':0, 'b':0, ..., 'z':0}

def getKeyFromValue(d, val):
    keys = [k for k, v in d.items() if v == val]
    keys = sorted(keys)
    if keys:
        return keys[0]
    else:
        return 'None'

for i in range(len(s_sorted)):
    alpha_dict[s_sorted[i]] += 1

print(getKeyFromValue(alpha_dict, 0))

Submission status: Accepted

Solution code:
import string
abc = list(string.ascii_lowercase)

s = input()
flag = 1

for i in abc:
    if i not in s:
        print(i)
        flag = 0
        break
if flag:
    print("None")

Submission status: Accepted

Solution code:
s = input()
s = ''.join(list(sorted(set(s))))
a = 'abcdefghijklmnopqrstuvwxyz'
if len(s) == 26:
  print('None')
else:
  for i in range(len(s)):
    if a[i] != s[i]:
      print(a[i])
      break
    if i == len(s)-1:
      print(a[i+1])

Submission status: Accepted

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

Submission status: Accepted

Solution code:
import string
letters=set(string.ascii_lowercase)
S=set(input())
print(min(letters-S or ["None"]))

Submission status: Accepted

Solution code:
s =input()
ab = [chr(97+i) for i in range(26)]
res = 'None'
for i in ab:
    if i not in s:
        res = i
        break
print(res)

Submission status: Accepted

Solution code:
import string
S = input()
al = string.ascii_lowercase

for a in al:
    if a not in S:
        print(a)
        break
else:
    print('None')

Submission status: Accepted

Solution code:
import sys
s = input()
s_set = set(s)
alpha = 'abcdefghijklmnopqrstuvwxyz'
for i in alpha:
    if i not in s_set:
        print(i)
        sys.exit()
print('None')

Submission status: Accepted

Solution code:
s = list(set(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"]
li = []
for i in range(len(a)):
  if a[i] not in s:
    li.append(a[i])
if len(li) == 0:
    print("None")
else:
    print(min(li))

Submission status: Accepted

Solution code:

s=input()
a=[0]*26
for i in range(len(s)):
	a[ord(s[i])-97]+=1
for i in range(26):
	if a[i]==0:
		print(chr(97+i))
		exit()
print("None")

Submission status: Accepted

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

Submission status: Accepted

Solution code:
S = input()
hantei = 0

serch = ('a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','y','z')

for i in range(0,25):
    if S.count(serch[i]) == 0 :
        hantei = 1
        print(serch[i])
        break

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

Submission status: Accepted

Solution code:
s = input()
l = [chr(ord("a")+i) for i in range(26)]
arr = {}
for i in l:
  arr[i] = False
for j in s:
  arr[j] = True
for k, v in sorted(arr.items()):
  if v == False:
    print(k)
    exit()
print("None")

Submission status: Accepted

Solution code:
S = input()

alp = 'abcdefghijklmnopqrstuvwxyz'
for i in alp:
    if not i in S:
        print(i)
        exit()
print('None')

Submission status: Accepted

Solution code:
S = input()

alp = 'abcdefghijklmnopqrstuvwxyz'
for i in alp:
    if i not in S:
        print(i)
        exit()
print('None')