Buggy python submission (verdict: Runtime Error):
s=set(list(input()))
a=set(list('abcdefghijklmnopqrstuvwxyz'))

if s==a:
    print('None')
else:
    b=a-s
    print(b[0])


Fixed submission:
s=set(list(input()))
a=set(list('abcdefghijklmnopqrstuvwxyz'))

if s==a:
    print('None')
else:
    b=sorted(list(a-s))
    print(str(b[0]))

Buggy python submission (verdict: Runtime Error):
s=set(list(input()))
a=list('abcdefghijklmnopqrstuvwxyz')
b=set()
for i in range(26):
    b=b.append(str(a[i]))
if s==b:
    print('None')
else:
    print(b-s)


Fixed submission:
s=set(list(input()))
a=set(list('abcdefghijklmnopqrstuvwxyz'))

if s==a:
    print('None')
else:
    b=sorted(list(a-s))
    print(str(b[0]))

Buggy python submission (verdict: Runtime Error):
s=set(list(input()))
a=list('abcdefghijklmnopqrstuvwxyz')
b=set()
for i in range(26):
    b.append(str(a[i]))
if s==b:
    print('None')
else:
    print(b-s)


Fixed submission:
s=set(list(input()))
a=set(list('abcdefghijklmnopqrstuvwxyz'))

if s==a:
    print('None')
else:
    b=sorted(list(a-s))
    print(str(b[0]))

Buggy python submission (verdict: Runtime Error):
s=set(list(input()))
a='abcdefghijklmnopqrstuvwxyz'
b=set()
for i in range(26):
    b.append(str(a[i]))
if s==b:
    print('None')
else:
    print(b-s)


Fixed submission:
s=set(list(input()))
a=set(list('abcdefghijklmnopqrstuvwxyz'))

if s==a:
    print('None')
else:
    b=sorted(list(a-s))
    print(str(b[0]))

Buggy python submission (verdict: Runtime Error):
s=set(sep(input()))
a='abcdefghijklmnopqrstuvwxyz'
b=set()
for i in range(26):
    b.append(str(a[i]))
if s==b:
    print('None')
else:
    print(b-s)


Fixed submission:
s=set(list(input()))
a=set(list('abcdefghijklmnopqrstuvwxyz'))

if s==a:
    print('None')
else:
    b=sorted(list(a-s))
    print(str(b[0]))

Buggy python submission (verdict: Runtime Error):
s=set(input().sep())
a='abcdefghijklmnopqrstuvwxyz'
b=set()
for i in range(26):
    b.append(str(a[i]))
if s==b:
    print('None')
else:
    print(b-s)


Fixed submission:
s=set(list(input()))
a=set(list('abcdefghijklmnopqrstuvwxyz'))

if s==a:
    print('None')
else:
    b=sorted(list(a-s))
    print(str(b[0]))

Buggy python submission (verdict: Runtime Error):
s=set(input())
a='abcdefghijklmnopqrstuvwxyz'
b=set()
for i in range(26):
    b.append(str(a[i]))
if s==b:
    print('None')
else:
    print(b-s)


Fixed submission:
s=set(list(input()))
a=set(list('abcdefghijklmnopqrstuvwxyz'))

if s==a:
    print('None')
else:
    b=sorted(list(a-s))
    print(str(b[0]))

Buggy python submission (verdict: Runtime Error):
s=set(input())
a='abcdefghijklmnopqrstuvwxyz'
b=set()
for i in range(26):
    b.append(a[i])
if s==b:
    print('None')
else:
    print(b-s)


Fixed submission:
s=set(list(input()))
a=set(list('abcdefghijklmnopqrstuvwxyz'))

if s==a:
    print('None')
else:
    b=sorted(list(a-s))
    print(str(b[0]))

Buggy python submission (verdict: Runtime Error):
s=set(input().split())
a='abcdefghijklmnopqrstuvwxyz'
b=set()
for i in range(26):
    b.append(a[i])
if s==b:
    print('None')
else:
    print(b-s)


Fixed submission:
s=set(list(input()))
a=set(list('abcdefghijklmnopqrstuvwxyz'))

if s==a:
    print('None')
else:
    b=sorted(list(a-s))
    print(str(b[0]))

Buggy python submission (verdict: Runtime Error):
s=set(input().split())
a='abcdefghijklmnopqrstuvwxyz'
b=set()
for i in range(26):
    b+=a[i]
if s==b:
    print('None')
else:
    print(b-s)


Fixed submission:
s=set(list(input()))
a=set(list('abcdefghijklmnopqrstuvwxyz'))

if s==a:
    print('None')
else:
    b=sorted(list(a-s))
    print(str(b[0]))

Buggy python submission (verdict: Runtime Error):
s=set(input().split())
a='abcdefghijklmnopqrstuvwxyz'
b=set()
for i in range(26):
    b+=a[i]
if s==b:
    print('None')
else:
    print(b-c)


Fixed submission:
s=set(list(input()))
a=set(list('abcdefghijklmnopqrstuvwxyz'))

if s==a:
    print('None')
else:
    b=sorted(list(a-s))
    print(str(b[0]))

Buggy python submission (verdict: Runtime Error):
s=set(input().split())
a=set('abcdefghijklmnopqrstuvwxyz')
a.split()
if s==a:
    print('None')
else:
    print(s-a)


Fixed submission:
s=set(list(input()))
a=set(list('abcdefghijklmnopqrstuvwxyz'))

if s==a:
    print('None')
else:
    b=sorted(list(a-s))
    print(str(b[0]))

Buggy python submission (verdict: Runtime Error):
s=set(input().split())
a=set(abcdefghijklmnopqrstuvwxyz)

if s==a:
    print('None')
else:
    print(s-a)

Fixed submission:
s=set(list(input()))
a=set(list('abcdefghijklmnopqrstuvwxyz'))

if s==a:
    print('None')
else:
    b=sorted(list(a-s))
    print(str(b[0]))