Problem:


Score : 200 points

Problem Statement

You are given a string S consisting of lowercase English letters.
Find the lexicographically (alphabetically) smallest lowercase English letter that does not occur in S.
If every lowercase English letter occurs in S, print None instead.

Constraints

1 \leq |S| \leq 10^5 (|S| is the length of string S.)

S consists of lowercase English letters.

Input

Input is given from Standard Input in the following format:

S

Output

Print the lexicographically smallest lowercase English letter that does not occur in S.
If every lowercase English letter occurs in S, print None instead.

Sample Input 1

atcoderregularcontest

Sample Output 1

b

The string atcoderregularcontest contains a, but does not contain b.

Sample Input 2

abcdefghijklmnopqrstuvwxyz

Sample Output 2

None

This string contains every lowercase English letter.

Sample Input 3

fajsonlslfepbjtsaayxbymeskptcumtwrmkkinjxnnucagfrg

Sample Output 3

d



Sample input:
atcoderregularcontest


Sample output:
b

Submission status: Accepted

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

Submission status: Accepted

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

Submission status: Accepted

Solution code:
s = input()

if len(set(s)) == 26:
  print("None")
else:
  for c in "abcdefghijklmnopqrstuvwxyz":
    if not c in set(s):
      break
  
  print(c)

Submission status: Accepted

Solution code:
S=input()

ans='None'
i=97
while i<=122:
    if chr(i)not in S:
        ans=chr(i)
        break
    i+=1

print(ans)

Submission status: Accepted

Solution code:
s = sorted(set(input()))
for i in range(97, 123):
    for j in range(len(s)):
        if s[j] == chr(i):
            break
    else:
        print(chr(i))
        break
else:
    print('None')

Submission status: Accepted

Solution code:
s = input().strip()

d = {
    '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 c in s:
    d[c] += 1

for c in sorted(d.keys()):
    if d[c] == 0:
        print(c)
        exit(0)

print('None')

Submission status: Accepted

Solution code:
import string

stg = input()
res = "None"
lets = {stg[0]}
if len(stg)>1:
  for i in range(1,len(stg)):
    lets.add(stg[i])
alpha = list(string.ascii_lowercase)
for i in alpha:
  if i not in lets:
    res = i
    break
print(res)

Submission status: Accepted

Solution code:
s = list(input())
for c in range(26):
    X = chr(ord('a') + c)
    if X not in s:
        print(X)
        exit()

print('None')

Submission status: Accepted

Solution code:
S=set(input())
arr=set(['a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'])
result=arr-S
if len(result)==0:
  print('None')
else:
  print(sorted(result)[0])

Submission status: Accepted

Solution code:
from sys import stdin


if __name__ == "__main__":
    _in = [_.rstrip() for _ in stdin.readlines()]
    S =     _in[0]   # type:str
    # vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
    s_arr = [s for s in S]
    s_arr = list(set(s_arr))
    if len(s_arr) == 26:
        s = 'None'
    else:
        s_arr.sort()
        for i in range(26):
            if len(s_arr) <= i:
                s = chr(i+97)
                break
            elif s_arr[i] != chr(i+97):
                s = chr(i+97)
                break
    # ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    print(s)

Submission status: Accepted

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

Submission status: Accepted

Solution code:
import string

def resolve():
    # 整数 1 つ
    s = input()
    # 整数複数個
    # a, b, c = list(map(int, input().split()))
    # 整数 N 個 (改行区切り)
    # N = [int(input()) for i in range(N)]
    # 整数 N 個 (スペース区切り)
    # N = list(map(int, input().split()))
    # 整数 (縦 H 横 W の行列)
    # A = [list(map(int, input().split())) for i in range(H)]

    alpha = string.ascii_lowercase
    A = [alpha[i] for i in range(len(alpha))]

    for x in A:
        if x not in s:
            print(x)
            break
        if x == "z":
            print("None")

resolve()

Submission status: Accepted

Solution code:
import sys
input = sys.stdin.readline
sys.setrecursionlimit(10**7)
from collections import Counter, deque
from collections import defaultdict
from itertools import combinations, permutations, accumulate, groupby, product
from bisect import bisect_left,bisect_right
from heapq import heapify, heappop, heappush
from math import floor, ceil,sqrt
from operator import itemgetter
def I(): return int(input())
def MI(): return map(int, input().split())
def LI(): return list(map(int, input().split()))
def LI2(): return [int(input()) for i in range(n)]
def MXI(): return [[LI()]for i in range(n)]
def printns(x): print('\n'.join(x))
def printni(x): print('\n'.join(list(map(str,x))))
inf = 10**17
mod = 10**9 + 7
#s=input().rstrip()

alphasm=[chr(i) for i in range(97, 97+26)]
s=input().rstrip()
s=list(s)
u=sorted(list(set(s)))
ans=0
for al in alphasm:
    if not (al in u):
        ans=al
        break
print(ans if ans!=0 else "None")

Submission status: Accepted

Solution code:
S = list(input())
A = [chr(ord('a') + i) for i in range(26)]
cnt = 0
for i in A:
  if i in S:
    continue
  else:
    print(i)
    cnt = 1
    break
if cnt == 0:
  print('None')

Submission status: Accepted

Solution code:
s = input()
g1 = set("abcdefghijklmnopqrstuvwxyz")
g2 = set(s)
a = g1 -g2
if a == set():
    print('None')
    

else:
    print(sorted(list(a))[0])

Submission status: Accepted

Solution code:
def main():
    S = input()
    st = list(map(lambda x: chr(97+x), range(26)))
    for ss in S:
        if ss in st:
            st.remove(ss)

    print(st[0] if len(st) > 0 else 'None')


if __name__ == "__main__":
    main()

Submission status: Accepted

Solution code:
a=[0 for i in range(26)]
s=input()
for i in range(len(s)):
    a[ord(s[i])-97]+=1
for i in range(26):
    if a[i]==0:
        print(chr(i+97))
        break
else:
    print(None)

Submission status: Accepted

Solution code:
from string import ascii_lowercase as abc
s = input()
if set(abc) == set(s):
    print('None')
else:
    print(sorted(list(set(abc)-set(s)))[0])

Submission status: Accepted

Solution code:
def resolve():
	s = input()
	t = [True]*26
	for i in s:
		t[ord(i) - 97] = False
	for i in range(26):
		if t[i]:
			print(chr(i+97))
			return
	print('None')
resolve()

Submission status: Accepted

Solution code:
S = input()
S = sorted(set(S))
S.append("0")
B =  ["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"]
i = 0
while True:
    if S[i] != B[i]:
        print(B[i])
        break
    i += 1
    if i == 26:
        print("None"  )
        break

Submission status: Accepted

Solution code:
S = input()
List = []
for i in range(len(S)):
  tmp = S[i]
  List.append(tmp)
List = list(set(List))
num2alpha = lambda c: chr(c+96)
for k in range(1,27):
  if(num2alpha(k) in List):
    pass
  else:
    print(num2alpha(k))
    exit()
print("None")

Submission status: Accepted

Solution code:
import string

s = input()

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

for x in lall:
    if x not in s:
        print(x)
        exit()
print("None")

Submission status: Accepted

Solution code:
S=input()
alphabet=[chr(i) for i in range(97, 97+26)]
ans=[]
for a in alphabet:
  if a not in S:
    ans.append(a)
if not ans:
  print('None')
else:
  print(ans[0])

Submission status: Accepted

Solution code:
s=sorted(set(input()))
for i in range(len(s)):
    s[i]=ord(s[i])
s.append("*")
x=0
a=97
while s[x]==a:
    x+=1
    a+=1
print(chr(a) if a<123 else None)

Submission status: Accepted

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

Submission status: Accepted

Solution code:
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"]
moji = str(input())
ans = "z"
cnt = 0
for i in range(26):
  if lst[i] not in moji and lst[i] <= ans:
    ans = lst[i]
    cnt += 1
if cnt > 0:
  print(ans)
elif cnt==0:
  print("None")

Submission status: Accepted

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

Submission status: Accepted

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

Submission status: Accepted

Solution code:
sset=set(input())

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

Submission status: Accepted

Solution code:
N=list(input())
a=[chr(i) for i in range(97, 97+26)]
d={a[i]:0 for i in range(len(a))}

for x in N:
    d[x]+=1
i=0
while i<=len(a)-1:
    if d[a[i]]==0:
        print(a[i])
        break
    i+=1
else:
    print('None')

Submission status: Accepted

Solution code:
import sys
def input(): return sys.stdin.readline().strip()

def resolve():
    s=set(input())
    alphabets=list(chr(ord('a')+i) for i in range(26))
    ans='None'
    for i in alphabets:
        if i not in s:
            ans=i
            break
    print(ans)
resolve()

Submission status: Accepted

Solution code:
s =list(input())
syurui = []
for i in s:
    if i not in syurui:
        syurui.append(i)
ans = sorted(syurui)
if len(ans)==26:
    print('None')
else:
    num = [97+i for i in range(26)]
    for i in num:
        if chr(i) not in ans:
            answer = i
            break
    print(chr(i))

Submission status: Accepted

Solution code:
s=set(list(input()))
if len(s)==26:print("None")
else:
    import string
    f="abcdefghijklmnopqrstuvwxyz"
    for i in list(f):
        if i not in s:print(i);exit()

Submission status: Accepted

Solution code:
s = input()
flag = [True]*26
for t in s:
    flag[ord(t)-ord('a')] = False
for i in range(26):
    if flag[i]:
        print(chr(i+ord('a')))
        break
else:
    print('None')

Submission status: Accepted

Solution code:
import sys
def input(): return sys.stdin.readline().strip()

def resolve():
    s=input()
    l='abcdefghijklmnopqrstuvwxyz'
    ans='None'
    for i in l:
        if i not in s:
            ans=i
            break
    print(ans)
resolve()

Submission status: Accepted

Solution code:
sset=set(input())

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

Submission status: Accepted

Solution code:
S = input()

import sys
for i in range(26):
    ans = chr(ord('a') + i)
    if not(ans in S):
        print(ans)
        sys.exit()
ans = "None"
print(ans)

Submission status: Accepted

Solution code:
import string

S = list(map(str, input()))
s = sorted(set(S))
count = 0

alphabet = string.ascii_lowercase

if len(s) == len(alphabet):
    print("None")

else:
    for i in range(len(s)):
        if s[i] != alphabet[i]:
            print(alphabet[i])
            break
        else:
            count += 1

if count == len(s):
    print(alphabet[len(s)])

Submission status: Accepted

Solution code:
S=input()
count={'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)):
    count[S[i]]+=1

ans=[]
for key, value in count.items():
    if value==0:
        ans.append(key)

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

Submission status: Accepted

Solution code:
import sys
## io ##
def IS(): return sys.stdin.readline().rstrip()
def II(): return int(IS())
def MII(): return list(map(int, IS().split()))
def MIIZ(): return list(map(lambda x: x-1, MII()))
## dp ##
def DD2(d1,d2,init=0): return [[init]*d2 for _ in range(d1)]
def DD3(d1,d2,d3,init=0): return [DD2(d2,d3,init) for _ in range(d1)]
## math ##
def to_bin(x: int) -> str: return format(x, 'b') # rev => int(res, 2)
def to_oct(x: int) -> str: return format(x, 'o') # rev => int(res, 8)
def to_hex(x: int) -> str: return format(x, 'x') # rev => int(res, 16)
MOD=10**9+7
def divc(x,y) -> int: return -(-x//y)
def divf(x,y) -> int: return x//y
def gcd(x,y):
    while y: x,y = y,x%y
    return x
def lcm(x,y): return x*y//gcd(x,y)
def enumerate_divs(n):
    """Return a tuple list of divisor of n"""
    return [(i,n//i) for i in range(1,int(n**0.5)+1) if n%i==0]
def get_primes(MAX_NUM=10**3):
    """Return a list of prime numbers n or less"""
    is_prime = [True]*(MAX_NUM+1)
    is_prime[0] = is_prime[1] = False
    for i in range(2, int(MAX_NUM**0.5)+1):
        if not is_prime[i]: continue
        for j in range(i*2, MAX_NUM+1, i):
            is_prime[j] = False
    return [i for i in range(MAX_NUM+1) if is_prime[i]]
## libs ##
from itertools import accumulate as acc
from collections import deque, Counter
from heapq import heapify, heappop, heappush
from bisect import bisect_left
#======================================================#

def main():
    s = set(IS())
    t = 'abcdefghijklmnopqrstuvwxyz'
    for ti in t:
        if not ti in s:
            print(ti)
            return None
    print('None')

if __name__ == '__main__':
    main()

Submission status: Accepted

Solution code:
s = set(input())
li = [chr(i) for i in range(97, 97+26)]
cnt = 0
for i in li:
    if i not in s:
        print(i)
        break
    else:
        cnt+=1
if cnt == 26:
    print("None")

Submission status: Accepted

Solution code:
s = set(list(input()))
if len(s)==26:
  print('None')
  exit()

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

Submission status: Accepted

Solution code:
s = [i for i in input()]
abc = [chr(i) for i in range(97,97+26)]
for p in s:
  try:
    abc.remove(p)
  except:
    pass
try:
  print(abc[0])
except:
  print("None")

Submission status: Accepted

Solution code:
S = list(input())
S_uniq = list(set(S))

a_z_list = list('abcdefghijklmnopqrstuvwxyz')
not_holding_sorted = sorted(list(set(a_z_list) - set(S)))

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

Submission status: Accepted

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

s=list(input())
s.sort()
for i in range(97,123):
    if s.count(chr(i))==0:
        print(chr(i))
        break
else:
    print("None")

Submission status: Accepted

Solution code:
S=input()
line="abcdefghijklmnopqrstuvwxyz"
ans="None"
for i in line:
    if i not in S:
        ans=i
        break
print(ans)

Submission status: Accepted

Solution code:
s = input()
sw = [0]*26
for t in s:
    sw[ord(t)-97] = 1
for i in range(26):
    if sw[i] == 0:
        print(chr(97+i))
        break
    if i == 25:
        print(None)

Submission status: Accepted

Solution code:
import numpy as np
import sys

input = sys.stdin.readline

S = list(input())

alp = list("abcdefghijklmnopqrstuvwxyz")

for a in alp:
    if a not in S:
        print(a)
        exit()

print("None")

Submission status: Accepted

Solution code:
import numpy as np
import sys

input = sys.stdin.readline

S = input()

S = sorted(list(set(S[:-1])))


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']


j = 0
for i in range(len(alpha)):
    if  S[j]== alpha[i] :
        if len(S)-1 != j:j+=1
    else:
        print(alpha[i])
        exit()


print("None")

Submission status: Accepted

Solution code:
s=list(input())
alp=list("abcdefghijklmnopqrstuvwxyz")
ans="None"
for w in alp:
    if w not in s:
        ans=w
        break
    else:
      pass
print(ans)

Submission status: Accepted

Solution code:
import collections
s = list(input())
c = collections.Counter(s)
p = list(c.items())
p.sort()
i=0
for k,v in p:
    if k == chr(ord("a")+i):
        i += 1
    else:
        print(chr(ord("a")+i))
        exit()
if i == 26:
    print("None")
else:
    print(chr(ord("a")+i))

Submission status: Accepted

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

Submission status: Accepted

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

Submission status: Accepted

Solution code:
w = str(input())
w =sorted(w)
import string
alp = str(string.ascii_lowercase)
c = []
for i in range(len(alp)): 
  c.append(0)
for i in range(len(alp)):
  W = alp[i]
  for j in range(len(w)):
    if W == w[j]:
      c[i] += 1
if c.count(0) == 0:
  print('None')
else:
  for i in range(len(c)):
    if c[i] == 0:
      print(alp[i])
      break

Submission status: Accepted

Solution code:
import numpy as np
S=input()
a_list = "abcdefghijklmnopqrstuvwxyz"
c_list = np.zeros(26)

for i in range(len(S)):
  c_list[a_list.index(S[i])] = c_list[a_list.index(S[i])] + 1

if not 0 in c_list: print('None')
else:
  c_list = c_list.tolist()
  print(a_list[c_list.index(0)])

Submission status: Accepted

Solution code:
s="qwertyuiopasdfghjklzxcvbnm"
l = sorted(list(s))
t = list(set(input()))
for i in l:
    if not i in t:
        print(i)
        break
else:
    print("None")

Submission status: Accepted

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

Submission status: Accepted

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

Submission status: Accepted

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

Submission status: Accepted

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

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

Submission status: Accepted

Solution code:
S = input()
wordNum = [0 for i in range(26)]
for wordOne in S:
    idx = ord(wordOne) - ord('a')
    wordNum[idx] += 1

ans = "None"
for i in range(26):
    if wordNum[i] == 0:
        ans = chr(ord('a') + i)
        break;

print(ans)

Submission status: Accepted

Solution code:
# ABC071B

s = input()
population = {chr(i) for i in range(ord('a'), ord('z')+1)}
ans = sorted(population - set(s))
if len(ans) == 0:
    print('None')
else:
    print(ans[0])

Submission status: Accepted

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

Submission status: Accepted

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

Submission status: Accepted

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

Submission status: Accepted

Solution code:
s=input()
S=list(set(s))
A=[]
cnt=124
for i in range(97,123):
  A.append(S.count(chr(i)))
#print(A)
if sum(A)==26:
  print('None')
else:
  print(chr(A.index(0)+97))

Submission status: Accepted

Solution code:
import string
s = input()
for a in string.ascii_lowercase:
    if a not in s:
        print(a)
        break
    if a =="z":
        print("None")
        break

Submission status: Accepted

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

Submission status: Accepted

Solution code:
#setの対称差を用いた方法
S = set(input()) #list()と同じで,set()も一発で行ける！
lists = set([chr(i) for i in range(ord('a'), ord('z')+1)])
ans = lists^S
print(min(ans) if len(list(ans)) != 0 else 'None')

Submission status: Accepted

Solution code:
S = list(map(str, input()))
S = set(S)
a = set(list('abcdefghijklmnopqrstuvwxyz'))
if len(list(a-S)) == 0:
  print('None')
else:
  print(sorted(list(a-S))[0])

Submission status: Accepted

Solution code:
S = set(input())
lists = set([chr(i) for i in range(ord('a'), ord('z')+1)])
ans = lists-S
print(min(ans) if len(list(ans)) != 0 else 'None')

Submission status: Accepted

Solution code:
alphabet = "abcdefghijklmnopqrstuvwxyz"
inputs = dict.fromkeys(set(input()))
chars = alphabet.translate(str.maketrans(inputs))
print(chars[0] if len(chars) > 0 else "None")

Submission status: Accepted

Solution code:
S = input()
list = []
for i in range(len(S)):
    list.append(S[i])
list = set(list)
lists = set([chr(i) for i in range(ord('a'), ord('z')+1)])
ans = lists-list
print('None' if len(ans)==0 else min(ans))

Submission status: Accepted

Solution code:
def resolve():
    B = input()
    b = set(B)
    for c in "abcdefghijklmnopqrstuvwxyz":
        if not c in b:
            print(c)
            return
    print("None")
            

if '__main__' == __name__:
    resolve()

Submission status: Accepted

Solution code:
S =input()

A = set(list('abcdefghijklmnopqrstuvwxyz'))
S = set(S)

if len(list(A-S)) == 0:
    print("None")
else:
    print (sorted(list(A-S))[0])

Submission status: Accepted

Solution code:
import sys

sys.setrecursionlimit(10 ** 7)
f_inf = float('inf')
mod = 10 ** 9 + 7


def resolve():
    s = set(input())
    for i in [chr(i) for i in range(97, 97 + 26)]:
        if i not in s:
            print(i)
            break
    else:
        print("None")


if __name__ == '__main__':
    resolve()

Submission status: Accepted

Solution code:
d = [chr(ord('a')+i) for i in range(26)]

S = input()

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

Submission status: Accepted

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

Submission status: Accepted

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

Submission status: Accepted

Solution code:
s = input()

alp = [True for _ in range(26)]

for c in s:
    alp[ord(c) - ord('a')] = False

for flag, i in zip(alp, range(26)):
    if flag:
        print(chr(ord('a') + i))
        exit()
print('None')

Submission status: Accepted

Solution code:
x = list(input())
i=0
while True:
	if i==26:
		print('None')
		break
	if not chr(ord('a')+i) in x:
		print(chr(ord('a')+i))
		break
	i+=1

Submission status: Accepted

Solution code:
# -*- coding: utf-8 -*-
import sys
sys.setrecursionlimit(10**9)
INF=10**18
MOD=10**9+7
input=lambda: sys.stdin.readline().rstrip()
YesNo=lambda b: bool([print('Yes')] if b else print('No'))
YESNO=lambda b: bool([print('YES')] if b else print('NO'))
int1=lambda x:int(x)-1

def main():
    S=set(input())
    a=ord('a')
    for i in range(26):
        if not chr(a+i) in S:
            print(chr(a+i))
            exit()
    print('None')

if __name__ == '__main__':
    main()

Submission status: Accepted

Solution code:
s = list(set(list(input())))
flag = True
for c in [chr(i) for i in range(97, 97+26)]:
    if c not in s:
        print(c)
        flag = False
        break
if flag:
    print('None')

Submission status: Accepted

Solution code:
from collections import defaultdict
import string

alf = string.ascii_lowercase

d = defaultdict(int)
S = ''.join(sorted(input()))
for v in alf:
    d[v] = 0

for i, v in enumerate(S):
    d[v] += 1
# print(sorted(d.items()))

sd = sorted(d.items())

count = 0
for v in sd:
    if(v[1] == 0):
        print(v[0])
        exit()
    else:
        count += 1
        continue

if (count == 26):
    print('None')

Submission status: Accepted

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

ans = list(ans - S)
if not ans:
    print("None")
else:
    ans.sort()
    print(ans[0])

Submission status: Accepted

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

Submission status: Accepted

Solution code:
s = list(input())
ss = list(set(s))
alp = [chr(ord("a")+i) for i in range(26)]
ans = "None"
for a in alp:
    if a in ss:
        continue
    else:
        ans = a
        break
print(ans)

Submission status: Accepted

Solution code:
import sys
readline = sys.stdin.buffer.readline
MOD = 10**9+7

def main():
    S = set(input())
    A = set('abcdefghijklmnopqrstuvwxyz')
    diff = A - S
    ans = list(diff)
    print(min(ans) if ans else 'None')


if __name__ == '__main__':
    main()

Submission status: Accepted

Solution code:
from sys import stdin
import sys

S = stdin.readline().rstrip()

for c in range(ord('a'), ord('z')+1):
    if S.find(chr(c)) == -1:
        print(chr(c))
        sys.exit()

print("None")

Submission status: Accepted

Solution code:
S = list(input())
minal = ord('z')
for i in range(ord('a'), ord('z')+1):
    if i < minal and chr(i) not in S:
        minal = i
list = set(S)
print(chr(minal) if len(list)!=26 else 'None')

Submission status: Accepted

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

Submission status: Accepted

Solution code:
s = input()

for i in range(26):
    if s.count(chr(ord("a") + i)) == 0:
        print(chr(ord("a") + i))
        exit()

print("None")

Submission status: Accepted

Solution code:
S = set(input())
def solve(S):
    for i in 'abcdefghijklmnopqrstuvwxyz':
        if not i in S:
            return i
    return 'None'
ans = solve(S)
print(ans)

Submission status: Accepted

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

Submission status: Accepted

Solution code:
alphabet = "abcdefghijklmnopqrstuvwxyz"

S = input()

result = ""
found = True

for i in alphabet:
    if i not in S:
        result = i
        found = False
        break

if not found:
    print(result)
else:
    print("None")

Submission status: Accepted

Solution code:
s = input()
alphabet = 'abcdefghijklmnopqrstuvwxyz'
for t in s:
	alphabet = alphabet.replace(t, '')
r = alphabet[0] if len(alphabet) > 0 else 'None'
print(r)

Submission status: Accepted

Solution code:
s = list(input())
set(s)
s.sort()
t = list("abcdefghijklmnopqrstuvwxyz")

for c in t:
  if c in s:
    continue
  else:
    print(c)
    exit()

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=set(input())
n=0
for i in alp:
  if i not in s:
    print(i)
    n=1
    break
if n==0:
  print('None')

Submission status: Accepted

Solution code:
S = input()

for i in range(26):
  if not chr(ord("a")+i) in S:
    print(chr(ord("a")+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:
import sys
import os
import math

ii = lambda: int(sys.stdin.buffer.readline().rstrip())
il = lambda: list(map(int, sys.stdin.buffer.readline().split()))
fl = lambda: list(map(float, sys.stdin.buffer.readline().split()))
iln = lambda n: [int(sys.stdin.buffer.readline().rstrip()) for _ in range(n)]

iss = lambda: sys.stdin.buffer.readline().decode().rstrip()
sl = lambda: list(map(str, sys.stdin.buffer.readline().decode().split()))
isn = lambda n: [sys.stdin.buffer.readline().decode().rstrip() for _ in range(n)]

MOD = 10 ** 9 + 7


def main():
    if os.getenv("LOCAL"):
        sys.stdin = open("input.txt", "r")

    T = set('abcdefghijklmnopqrstuvwxyz')
    S = set(iss())
    s = sorted(T ^ S)
    print(s[0] if len(s) > 0 else 'None')



if __name__ == '__main__':
    main()

Submission status: Accepted

Solution code:
s = input()

alpha = [chr(i) for i in range(97,123)]

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

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

Submission status: Accepted

Solution code:
exist = True
s = list(input())
e_l = [chr(i) for i in range(97, 97+26)]
for i in e_l:
    if i not in s:
        exist = False
        break
if exist:
    print('None')
else:
    print(i)

Submission status: Accepted

Solution code:
l=list(ord(c) for c in input())
sample=list(range(97,123))
diff=list(sorted(set(sample).difference(l)))
if len(diff)>0:
    print (chr(diff[0]))
else:
    print ('None')

Submission status: Accepted

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


if __name__ == '__main__':
    main()

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()
set_s = set(s)

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

ans_li = sorted([a for a in alphabet_li if a not in set_s])

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

Submission status: Accepted

Solution code:
S = input()

al = 'abcdefghijklmnopqrstuvwxyz'

ans = ''

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

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 = set(input())
l = list("abcdefghijklmnopqrstuvwxyz")
for i in s:
    l.remove(i)
if l == []:
    print("None")
else:
    print(l[0])

Submission status: Accepted

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

moji = [chr(i) for i in range(97,97+26)]
for i in range(len(moji)):
    if not(moji[i] in set_s):
        print(moji[i])
        quit()
print("None")

Submission status: Accepted

Solution code:
s = input()
set_s = set(s)
if len(set_s) == 26:
    print("None")
    quit()
moji = [chr(i) for i in range(97,97+26)]
for i in range(len(moji)):
    if not(moji[i] in set_s):
        print(moji[i])
        quit()

Submission status: Accepted

Solution code:
S = input()
alphabet = [chr(ord("a") + i) for i in range(26)]
ans = "None"

for c in alphabet:
    if c not in S:
        ans = c
        break

print(ans)

Submission status: Accepted

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

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

Submission status: Accepted

Solution code:
s=input()
lowercase = 'abcdefghijklmnopqrstuvwxyz'
count=0
for moji in lowercase:
  if moji not in s:
    print(moji)
    break
else:
  print('None')

Submission status: Accepted

Solution code:
S = input()
S = set([s for s in S])

if len(S) == 26:
    print('None')
else:
    for i in range(97, 123):
        if chr(i) not in S:
            print(chr(i))
            break