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: Wrong Answer

Solution code:
s=list(set(input()))
test=["a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"]
test.sort()
s.sort()
if len(s)==len(test):
    print("None")
    exit()
print(test)
print(s)
i=0
while True:
    if len(s)<=i:
        print(test[i])
        break
        
    if test[i]!=s[i]:
        print(test[i])
        break
    i+=1

Submission status: Wrong Answer

Solution code:
s=list(set(input()))
test=["a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"]
test.sort()
s.sort()
if len(s)==len(test):
    print("None")
    exit()
print(test)
print(s)
i=0
while True:
    if len(s)<=i:
        print(test[i])
        exit()
        
    if test[i]!=s[i]:
        print(test[i])
        break
    i+=1

Submission status: Wrong Answer

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

s = list(input())
s.sort()

prev = ord("a")
ans = "None"
for i in range(1, len(s)):
    if ord(s[i]) - prev > 1:
        ans = chr(prev + 1)
        break
    else:
        prev = ord(s[i])
print(ans)

Submission status: Wrong Answer

Solution code:
alp = "a b c d e f g h i j k l m n o p q r s t u v w x y z"
alp = list(map(str, alp.split()))
s = input()
for i in range(len(s)):
    for j in range(26):
        if(s[i] == alp[j]):
            alp[j] = "?"
while("?" in alp):
    alp.remove("?")
if(len(alp) == 0):
    print("None")
else:
    print(alp)

Submission status: Wrong Answer

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

Submission status: Wrong Answer

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

Submission status: Wrong Answer

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

Submission status: Wrong Answer

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

Submission status: Wrong Answer

Solution code:
if __name__ == '__main__':
    S = input()
    dic = [chr(i) for i in range(97, 123)]
    for i in range(len(dic)):
        if dic[i] not in S:
            print(dic[i])
            break

Submission status: Wrong Answer

Solution code:
a=raw_input()
for i in range(97,26):
 if chr(i) in a:
  print chr(i)
print "None"

Submission status: Wrong Answer

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

if not found:
    print('None')

Submission status: Wrong Answer

Solution code:
S = input()
alphabet = "abcdefghijklmnopqrstuvwxyz"
for i in alphabet:
  if i not in S:
    print(i)
    quit()
  else:
    print('None')

Submission status: Wrong Answer

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

Submission status: Wrong Answer

Solution code:
# -*- encoding: utf-8 -*-
s = list(input().rstrip())
alpha = list(map(chr, range(ord('a'), ord('z'))))
 
for a in alpha:
    if a not in s:
        print(a)
        break
else:
    print("None")

Submission status: Wrong Answer

Solution code:
s=set(input())
eng = [chr(i) for i in range(97,123)]
for i in eng:
    if i not in s:
        print(i)
        break

Submission status: Wrong Answer

Solution code:
#文字列をセット
str = input()
flag = 0
result = "None"
#小文字のアルファベットをセット
for s in str:
    for i in range(97, 97+26):
        if flag == 0:
            if  chr(i) == s:
                result = chr(i)
                flag = 1
        else:
            break
print(result)

Submission status: Wrong Answer

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

Submission status: Wrong Answer

Solution code:
s = input()
p = set()
c = s[0]
for i in s:
    c = min(c, i)
    p.add(i)

if len(p) >= 26:
    print('None')
else:
    print(c)

Submission status: Wrong Answer

Solution code:
s=input()

c = s[0]
for i in s:
    c = min(c, i)

if c == 'a':
    print('None')
else:
    print(c)

Submission status: Wrong Answer

Solution code:
s = input()

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

for v in l:
	if v in s:
		continue
	else:
		print(v)
		break

Submission status: Wrong Answer

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

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

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


solve()

Submission status: Wrong Answer

Solution code:
def solve(): # 071B - Not Found
    alphabet = []
    for i in range(26):
        alphabet.append(chr(97 + i))
    s = list(input())
    
    for j in s:
        if j in alphabet:
            alphabet.remove(j)
        else:
            pass
        
    if len(alphabet) == 0:
        print("NONE")
    else:
        print(alphabet[0])


if __name__ == '__main__':
    solve()

Submission status: Wrong Answer

Solution code:
import sys
line = raw_input()
res = dict()
for i in line:
    res[i] = 1
    if len(res) == 26:
        print 'None'
        sys.exit(0)
for i in 'abcdefghijklmnopqrstuvwxyz':
    if res.get(i, None) is not None:
        print i
        sys.exit(0)

Submission status: Wrong Answer

Solution code:
import sys
line = raw_input()
res = dict()
for i in line:
    if len(res) == 26:
        print 'None'
        sys.exit(0)
    res[i] = 1
for i in 'abcdefghijklmnopqrstuvwxyz':
    if res.get(i, None) is not None:
        print i
        sys.exit(0)

Submission status: Wrong Answer

Solution code:
import sys

alphabet = "abcdefghijklmnopqrstuvwxyz"
word = raw_input()

for letter in alphabet:
    if letter not in word:
        break

if letter == "z":
    print "None"
else:
    print letter

Submission status: Wrong Answer

Solution code:
import sys

alphabet = "abcdefghijklmnopqrstuvwxyz"
word = raw_input()

for letter in alphabet:
    if letter not in word:
        break

if letter == "z":
    print None
else:
    print letter

Submission status: Wrong Answer

Solution code:
s = raw_input()
lst = []
for i in range(98,123):
    x = chr(i)
    if (x in s) == False:
        lst.append(x)
if len(lst) == 0:
    print 'None'
else:
    print min(lst)

Submission status: Wrong Answer

Solution code:
#ABC071B
import sys

s=raw_input()
l=[False for i in xrange(26)]
for i in xrange(len(s)):
 temp=ord(s[i])-97
 l[temp]=True
if len(set(s))==26:
 print 'None'
 sys.exit()
for i in xrange(26):
 if l[i]:
  print chr(i+97)
  break

Submission status: Wrong Answer

Solution code:
import string

a = input()

for i in string.ascii_lowercase:
    if i not in a:
        print(i)
        break

Submission status: Wrong Answer

Solution code:
s = input()
s_list = list(set(s))
s_list.sort()
char_list =  ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'n', 'm','o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z']

if len(s_list) == 26:
    print('None')
elif s_list == ['a']:
    print('b')
elif len(s_list) ==0:
    print('a')
elif len(s_list) ==1:
    print('a')
else:
    for i in range(26):
        if s_list[i] != char_list[i+1]:
            print(str(char_list[i+1]))
            break

Submission status: Wrong Answer

Solution code:
S = 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']

n = 0

for i in range(26):

	if alpha[n] not in S:
		print(alpha[n])
		break
	if n == 26:
		print("None")
		
	n += 1

Submission status: Wrong Answer

Solution code:
S = 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']

n = 0

for i in range(26):

	if alpha[n] not in S:
		print(alpha[n])
		break
	if n == 25:
		print("None")
		
	n += 1

Submission status: Wrong Answer

Solution code:
s = input()
s_list = list(set(s))
s_list.sort()
char_list =  ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'n', 'm','o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z']

if len(s_list) == 26:
    print('None')
elif s_list == ['a']:
    print('b')
elif len(s_list) ==0:
    print('a')
elif len(s_list) ==1:
    print('a')
else:
    for i in range(25):
        if s_list[i] != char_list[i+1]:
            print(str(char_list[i]))
            break

Submission status: Wrong Answer

Solution code:
st = input()
hash_set = set()
for item in st:
    hash_set.add(item)

a = "abcdefghijklmnopqrstuvwxyz"

flag = False
for item in a:
    if item in hash_set:
        print(item)
        flag = True
        break

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

Submission status: Wrong Answer

Solution code:
S = raw_input()
ss = set(S)
ans = set("abcdefghijklmnopqrstuvwxyz").difference(ss)

if len(ans): print(ans.pop())
else: print("None")

Submission status: Wrong Answer

Solution code:
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']

n = 0
m = 0

for i in range(26):

	if alpha[n] not in S:
		print(alpha[n])
		break
	if n == 26:
		m = 1
		break
		
	n += 1
	
if m == 1:
	print('None')

Submission status: Wrong Answer

Solution code:
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']

n = 0
m = 0

for i in range(26):

	if alpha[n] not in S:
		print(alpha[n])
		break
	if n == 25:
		m = 1
		break
		
	n += 1
	
if m == 1:
	print('None')

Submission status: Wrong Answer

Solution code:
s = input()
s_list = list(set(s))
s_list.sort()
char_list =  ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'n', 'm','o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z']

if len(s_list) == 26:
    print('None')
elif len(s_list) ==0:
    print('a')
else:
    for i in range(26):
        if str(s_list[i]) != str(char_list[i]):
            print(str(char_list[i]))
            break

Submission status: Wrong Answer

Solution code:
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']

n = 0
m = 0

for i in range(26):

	if alpha[n] not in S:
		print(alpha[n])
		break
	if n == 26:
		m = 1
		
	n += 1
	
if m == 1:
	print('None')

Submission status: Wrong Answer

Solution code:
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']

n = 0
m = 0

for i in range(26):

	if alpha[n] not in S:
		print(alpha[n])
	if n == 26:
		m = 1
		
	n += 1
	
if m == 1:
	print('None')

Submission status: Wrong Answer

Solution code:
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']

n = 0
m = 0

for i in range(26):

	if alpha[n] not in S:
		print(alpha[n])
	if n == 25:
		m = 1
		
	n += 1
	
if m == 1:
	print('None')

Submission status: Wrong Answer

Solution code:
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']

n = 0
m = 0

for i in range(26):
	if n == 25:
		m = 1

	if alpha[n] not in S:
		print(alpha[n])
		break
		
	n += 1
	
if m == 1:
	print('None')

Submission status: Wrong Answer

Solution code:
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']

n = 0
m = 0

for i in range(26):
	if alpha[n] not in S:
		print(alpha[n])
		break
		if n == 25:
			m = 1
	n += 1
	
if m == 1:
	print('None')

Submission status: Wrong Answer

Solution code:
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']

n = 0
m = 0

for i in range(26):
	if alpha[n] not in S:
		print(alpha[n])
		break
		if n == len(S):
			m = 1
	n += 1
	
if m == 1:
	print('None')

Submission status: Wrong Answer

Solution code:
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']

n = 0
m = 0

for i in range(len(S)):
	if alpha[n] not in S:
		print(alpha[n])
		break
	n += 1
	
	if n == len(S) :
		m = 1
		

if m == 1:
	print('None')

Submission status: Wrong Answer

Solution code:
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']

n = 0
m = 0

for i in range(len(S)):
	if alpha[n] not in S:
		print(alpha[n])
		break
	n += 1
	
	if n == len(S) - 1:
		m = 1
		

if m == 1:
	print('None')

Submission status: Wrong Answer

Solution code:
string=input()
l="abcdefghijklmnopqrstuvwxyz"
for i in l:
    if i not in string:
        print(i)
        break
else:
    print("none")

Submission status: Wrong Answer

Solution code:
s=input()
char=['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']
check=False
for c in char:
    if not c in s:
        print(c,end='')
        check=True
if  check==False:
    print('None',end='')

Submission status: Wrong Answer

Solution code:
s=input()
check=False
for c in r'[a-z]':
    if not c in s:
        print(c,end='')
        check=True
if  check==False:
    print('None',end='')

Submission status: Wrong Answer

Solution code:
s = input()
s_list = list(set(s))
s_list.sort()
char_list =  ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'n', 'm','o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z']

if len(s_list) == 26:
    print('None')
else:
    for i in range(26):
        if str(s_list[i]) != str(char_list[i]):
            print(str(char_list[i]))
            break

Submission status: Wrong Answer

Solution code:
S = input()
a = 'abcdefghijklmnopqrstuvwxyz'
a = 'abcdefghijklmnopqrstuvwxyz'
for aa in a:
    if aa in S:
        pass
    else:
        print(aa)
        break

Submission status: Wrong Answer

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

S = input()
CHR = [chr(i) for i in range(97, 97+26)]

judge = 1
i = 0

while(judge > 0 and i < 26):
    judge = S.count(CHR[i])
    i = i+1

if(i<25):
    print(CHR[i-1])
else:
    print("None")

Submission status: Wrong Answer

Solution code:
S = input()
count = [0]*26 
b = 1 ### NONEフラグ

for i in S:
	count[ord(i)-97] == 1
	
for i in count:
	if count[i] == 0:
		print(chr(97+i))
		b = 0
		break

if b == 1:
	print("None")

Submission status: Wrong Answer

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


if s in test:
    print("None")
else:
    for i in test:
        if i in s:
            continue
        else:
            print(i)
            break

Submission status: Wrong Answer

Solution code:
alphabet_list = [0 for x in range(ord('a'),ord('z')+1)]

S = list(raw_input())

for x in S:
    alphabet_list[ord(x) - ord('a')] += 1

print_flag = False
for index in range(0,ord('z')-ord('a')):
    if alphabet_list[index] == 0:
        print(chr(index+ord('a')))
        print_flag = True
        break

if not(print_flag):
    print('None')

Submission status: Wrong Answer

Solution code:
S = raw_input()

for i in range(0,25):
    if S.find(chr(i+97))==-1 :
        print chr(i+97)
        break

Submission status: Wrong Answer

Solution code:
S = 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"]
S = list(set(S))
S.sort()
#print(len(S))
for i in range(len(S)):
    if len(S) == 25 and i == 24:
        print("z")
    if S[i] != alpha[i]:
        print(alpha[i])
        break
    elif i == 25:
        print("None")

Submission status: Wrong Answer

Solution code:
S = input()
d = {}

for i in range(ord("a"), ord("z")):
    d[chr(i)] = False

for c in S:
    d[c] = True

ans = "None"
for i in range(ord("a"), ord("z")):
    if not d[chr(i)]:
        ans = chr(i)
        break
print(ans)

Submission status: Wrong Answer

Solution code:
#! -*- coding:utf-8 -*-
s = str(input())
s = list(s)
x = 'abcdefghijklmnopqrstuvwxyz'
x = list(x)
print(s)

flag = 0
for i in range(len(s)):
    try:
        if(len(x) == 1 and s[i] == x[0]):
            flag = 1
        x.remove(s[i])
    except:
        pass

if(flag == 1):
    print('None')
else:
    print(x[0])

Submission status: Wrong Answer

Solution code:
s = input()
ab_list = [True]*26
for i in s:
  ab_list[ord(i)-97] = False
for i in range(len(ab_list)):
  if ab_list[i]:
    print(chr(i+97))
    break

Submission status: Wrong Answer

Solution code:
s = set(list(input()))
check = list("qwertyuiopasdfghjklzxcvbnm")
check.sort()
for i in check:
    if i not in s:
        print(i)
        break

Submission status: Wrong Answer

Solution code:
d = raw_input()

d_list = []
for i in range(len(d)):
    d_list.append(ord(d[i]))

ans = ord('a')
while True:
    if ans not in d_list:
        break
    if ans > ord('a')+112:
        break
    ans += 1
    
if ans > 112:
    print 'None'
else:
    print chr(ans)

Submission status: Wrong Answer

Solution code:
s = input()
s_list = list(s)
s_set = s_list
abc_list = [chr(i) for i in range(97, 97+26)]
if len(s_set) == 26:
    print("None")
else:
    for a in abc_list:
        if a in s_set:
            pass
        else:
            print(a)
            break

Submission status: Wrong Answer

Solution code:
S = 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"]
S = list(set(S))
S.sort()
for i in range(len(S)):
    if S[i] != alpha[i]:
        print(alpha[i])
        break
    elif i == 25:
        print("None")

Submission status: Wrong Answer

Solution code:
import sys
inp = lambda t: t(sys.stdin.readline().strip())
inpm = lambda t: map(t, sys.stdin.readline().split())
inpl = lambda t: list(map(t, sys.stdin.readline().split()))

s = inp(str)

p = 'a'
for i in s:
	if i == p:
		p = chr(ord(p) + 1)

if ord(p) > ord('z'):
	print('None')
else:
	print(p)

Submission status: Accepted

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

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

Submission status: Accepted

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

Submission status: Accepted

Solution code:
S = [s for s in input()]
li = list(set(S))
li.sort()

ans = 'None'
for c in [chr(c) for c in range(97, 123)]:
    if c not in li:
        ans = c
        break
print(ans)

Submission status: Accepted

Solution code:
S = set(list(input()))
cf = [chr(ord("a")+i) for i in range(26)]

for i in range(len(cf)):
    if cf[i] not in S:
        print(cf[i])
        exit()
print("None")

Submission status: Accepted

Solution code:
S = str(input())
al = [chr(ord('a') + i) for i in range(26)]
data = []
for x in S:
    if not x in data:
        data.append(x)
ans = list(set(al) ^ set(data))
ans.sort()
if len(ans) == 0:
    print('None') 
else:
    print(ans[0])

Submission status: Accepted

Solution code:
import sys
s = input()

for i in range(97, 123):
    st = chr(i)
    if st not in s:
        print(st)
        sys.exit()

    
print(None)

Submission status: Accepted

Solution code:
from string import ascii_lowercase


def answer(s: str) -> str:
    not_in_s = list(set(ascii_lowercase) - set(s))
    if not not_in_s:
        return 'None'
    not_in_s.sort()

    return not_in_s[0]


def main():
    s = input()
    print(answer(s))


if __name__ == '__main__':
    main()

Submission status: Accepted

Solution code:
s = input()

alphabets = 'abcdefghijklmnopqrstuvwxyz'

for x in alphabets:
    if x in s:
        continue
    else:
        print(x)
        break
else:
    print('None')

Submission status: Accepted

Solution code:
s = input()
ans = 'None'
line = [0 for i in range(26)]
for i in s:
  line[ord(i)-97] += 1
for j in range(26):
  if line[j] == 0:
    ans = chr(j + 97)
    break
print(ans)

Submission status: Accepted

Solution code:
import string
s = input()
t = set(s) ^ set(string.ascii_lowercase)

for i in string.ascii_lowercase:
  if set(i) & t:
    print(i)
    break
else:
  print("None")

Submission status: Accepted

Solution code:
import string

s = list(map(str, input()))
s = list(set(s))
s.sort()

ans = ""
arr = []

alp = list(map(str, string.ascii_lowercase))
for char in s:
    alp.remove(char)

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

Submission status: Accepted

Solution code:
s = list(input())
import collections
import sys
a = collections.Counter(s)

for i in range(97,97+26):
    if chr(i) not in a:
        print(chr(i))
        sys.exit()
else:
    print("None")

Submission status: Accepted

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

Submission status: Accepted

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

Submission status: Accepted

Solution code:
A = ['a','s','d','f','g','h','j','k','l','z','x','c','v','b','n','m','q','w','e','r','t','y','u','i','o','p']
S = list(set(input()))
for i in S:
    A.remove(i)
A.sort()
try:
    print(A[0])
except:
    print("None")

Submission status: Accepted

Solution code:
import string
L = ['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 L:
  if i not in S:
    print(i)
    break
else:
  print(None)

Submission status: Accepted

Solution code:
import string
S = set(input())
for i in range(97, 123):
  s = chr(i)
  if s not in S:
    print(s)
    break
else:
  print(None)

Submission status: Accepted

Solution code:
S = list(input())
a = list("abcdefghijklmnopqrstuvwxyz")
for i in S:
    if i in a:
        a.remove(i)

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

Submission status: Accepted

Solution code:
s = list(map(str,input()))
alp = "abcdefghijklmnopqrstuvwxyz"
s = set(s)
for i in range(26):
  if alp[i] not in s:
    print(alp[i])
    exit()
  elif i == 25:
    print("None")

Submission status: Accepted

Solution code:
s = set(input())

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

Submission status: Accepted

Solution code:
s = input()
alphabets = [0] * 26

for i in s:
    alphabets[ord(i) - ord("a")] += 1

for i in range(26):
    if alphabets[i] == 0:
        print(chr(i + ord("a")))
        break
else:
    print("None")

Submission status: Accepted

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

Submission status: Accepted

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

Submission status: Accepted

Solution code:
s = input()

alphabets = 'abcdefghijklmnopqrstuvwxyz'

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

print('None')

Submission status: Accepted

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

Submission status: Accepted

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

Submission status: Accepted

Solution code:
import re
s = str(input())
l = list('abcdefghijklmnopqrstuvwxyz')

for i in l:
    if not re.search(i,s):
        print(i)
        break
else:
    print('None')

Submission status: Accepted

Solution code:
import string

S = set(input())

result = ''
for i in string.ascii_lowercase:
    if i not in S:
        print(i)
        break
else:
    print('None')

Submission status: Accepted

Solution code:
s = input()
r = set(map(chr, range(97, 97+26)))
r = r - set(s)
if len(r) == 0:
    print('None')
else:
    r = min(r)
    print(r)

Submission status: Accepted

Solution code:
import sys
S = list(input())
s = list(set(S))
s.sort()
alfa = list('abcdefghijklmnopqrstuvwxyz')
ans = 0
if(len(s)==len(alfa)):
  print('None')
  sys.exit()
else:
  for i in range(len(s)):
    if(s[i]!=alfa[i]):
      print(alfa[i])
      sys.exit()
  print(alfa[len(s)])

Submission status: Accepted

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

Submission status: Accepted

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

Submission status: Accepted

Solution code:
s=input()
f=1
for i in 'abcdefghijklmnopqrstuvwxyz':
    if i not in s:
        print(i)
        f=0
        exit()
if f:print('None')

Submission status: Accepted

Solution code:
#from statistics import median
#import collections
#aa = collections.Counter(a) # list to list || .most_common(2)で最大の2個とりだせるお a[0][0]
from math import gcd
from itertools import combinations,permutations,accumulate, product # (string,3) 3回
#from collections import deque
from collections import deque,defaultdict,Counter
import decimal
import re
import math
import bisect
import heapq
#
#
#
# pythonで無理なときは、pypyでやると正解するかも！！
#
#
# my_round_int = lambda x:np.round((x*2 + 1)//2)
# 四捨五入g
#
# インデックス系
# int min_y = max(0, i - 2), max_y = min(h - 1, i + 2);
# int min_x = max(0, j - 2), max_x = min(w - 1, j + 2);
#
#
import sys
sys.setrecursionlimit(10000000)
mod = 10**9 + 7
#mod = 9982443453
#mod = 998244353
INF = float('inf')
from sys import stdin
readline = stdin.readline
def readInts():
  return list(map(int,readline().split()))
def readTuples():
    return tuple(map(int,readline().split()))
def I():
    return int(readline())
s = input()
lis = "abcdefghijklmnopqrstuvwxyz"
for i in range(len(lis)):
    if lis[i] in s:
        pass
    else:
        print(lis[i])
        exit()
print('None')

Submission status: Accepted

Solution code:
S = list(input())
A = list('abcdefghijklmnopqrstuvwxyz')
ans = 'None'
for a in A:
    if a not in S:
        ans = a
        break
print(ans)

Submission status: Accepted

Solution code:
from collections import Counter
S = list(input())
S = Counter(S)
if len(S) == 26:
    ans = "None"
else:
    A = [chr(i) for i in range(97, 97+26)]
    for i in A:
        if i in S:
            continue
        ans = i
        break
print(ans)

Submission status: Accepted

Solution code:
import sys
# sys.setrecursionlimit(100000)


def input():
    return sys.stdin.readline().strip()


def input_int():
    return int(input())


def input_int_list():
    return [int(i) for i in input().split()]


def main():
    S = input()
    for i in range(ord("a"), ord("z") + 1):
        if chr(i) not in S:
            print(chr(i))
            return
    print("None")
    return


if __name__ == "__main__":
    main()

Submission status: Accepted

Solution code:
S = input()
ans = "None"
for i in range(97, 123):
  alp = chr(i)
  if alp not in S:
    ans = alp
    break
print(ans)

Submission status: Accepted

Solution code:
S = input().strip()
C = {chr(i):0 for i in range(97,123)}
for i in range(len(S)):
    C[S[i]] += 1
flag = 0
a = 0
for i in range(97,123):
    if C[chr(i)]==0:
        a = chr(i)
        flag = 1
        break
if flag==1:
    print(a)
else:
    print("None")

Submission status: Accepted

Solution code:
S = input()
l = sorted(list(set(S)))

ans = ""
for i in range(len(l)):
  if ord(l[i]) !=  97 + i:
    ans = chr(97+i)
    break
  elif i == 25 and l[i] == "z":
    ans = "None"

if ans != "":
 print(ans)
else:
  print(chr(ord(l[-1])+1))

Submission status: Accepted

Solution code:
s = list(str(input()))
l = set(s)
for i in range(26):
    c = chr(ord('a')+i)
    if c not in l:
        print(c)
        exit()
else:
    print('None')

Submission status: Accepted

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

Submission status: Accepted

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

Submission status: Accepted

Solution code:
# 35
import string

S = str(input())

set1 = set()
for s in S:
    set1.add(s)

set2 = set()
for alf in string.ascii_lowercase:
    set2.add(alf)

list = sorted(set2 - set1)
if not list: print('None')
else: print(sorted(list)[0])

Submission status: Accepted

Solution code:
#-*-coding:utf-8-*-
import sys
input=sys.stdin.readline

def main():
    alpha_data={}
    S = input()
    [alpha_data.update({chr(i):0}) for i in range(97, 97+26)]
    
    for s in S:
        if s in alpha_data:
            tmp=alpha_data[s]
            tmp+=1
            alpha_data[s]=tmp
        else:
            continue
    for i,v in alpha_data.items():
        if v==0:
            print(i)
            exit()
    print("None")

if __name__=="__main__":
    main()

Submission status: Accepted

Solution code:
S = list(input())
alpha = 'abcdefghijklmnopqrstuvwxyz'

for a in alpha:
  if S.count(a) == 0:
    print(a)
    break
else:
  print("None")

Submission status: Accepted

Solution code:
s = input()
alpabet = [chr(x) for x in range(97,123)]
try:
    for a in alpabet:
        s.index(a)
    else:
        print(None)
except ValueError as e:
    print(a)

Submission status: Accepted

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

for c in T:
    if S.count(c)==0:
        print(c)
        break;
else:
    print("None")