Buggy python submission (verdict: Runtime Error):

s = list(input())
k = int(input())
ansnum = 0

for j in range(k):
    # listj = []
    # for i in range(len(s)-j):
    #     #print(s[i:i+j+1])
    #     listj.append(s[i:i+j+1])
    listj = [s[i:i + j + 1] for i in range(len(s) - j)]
    listj.sort()
    # print('listj:',listj)
    # print('j:',j)
    if len(listj) >= 2 and listj[0] == listj[1]:
        # print('choufuku')
        pass
    else:
        # j+1文字で重複なしの場合(j=0,1,2,3,4)
        s = ''.join(s)
        lens = len(s)
        for i in range(len(listj)):
            num = s.index(''.join(listj[i]))
            a = lens - num
            # print('index:',num)
            # print('ansnum:',ansnum)
            if a < k - ansnum:
                ansnum += a
            else:
                ans = s[num:num + k - ansnum]
                ansnum = k + 1
                break
#print('ans:',ans)
print(ans)

Fixed submission:
s = list(input())
k = int(input())
subs = []
for i in range(min(k,len(s))):
  for j in range(len(s)-i):
    subs.append(''.join(s[j:j+i+1]))
subs = list(set(subs))
subs.sort()
#print(subs)
print(subs[k-1])

Buggy python submission (verdict: Runtime Error):
s = list(input())
k = int(input())
ansnum = 0

for j in range(k):
    # listj = []
    # for i in range(len(s)-j):
    #     #print(s[i:i+j+1])
    #     listj.append(s[i:i+j+1])
    listj = [s[i:i + j + 1] for i in range(len(s) - j)]
    listj.sort()
    # print('listj:',listj)
    # print('j:',j)
    if len(listj) >= 2 and listj[0] == listj[1]:
        # print('choufuku')
        pass
    else:
        # j+1文字で重複なしの場合(j=0,1,2,3,4)
        s = ''.join(s)
        lens = len(s)
        for i in range(len(listj)):
            num = s.index(''.join(listj[i]))
            a = lens - num
            # print('index:',num)
            # print('ansnum:',ansnum)
            if a < k - ansnum:
                ansnum += a
            else:
                ans = s[num:num + k - ansnum]
                ansnum = k + 1
                break
    if ansnum > k:
        break

#print('ans:',ans)
print(ans)

Fixed submission:
s = list(input())
k = int(input())
subs = []
for i in range(min(k,len(s))):
  for j in range(len(s)-i):
    subs.append(''.join(s[j:j+i+1]))
subs = list(set(subs))
subs.sort()
#print(subs)
print(subs[k-1])

Buggy python submission (verdict: Runtime Error):
s = list(input())
k = int(input())
ansnum = 0

for j in range(k):
    # listj = []
    # for i in range(len(s)-j):
    #     #print(s[i:i+j+1])
    #     listj.append(s[i:i+j+1])
    listj = [s[i:i + j + 1] for i in range(len(s) - j)]
    listj.sort()
    # print('listj:',listj)
    # print('j:',j)
    if len(listj) >= 2 and listj[0] == listj[1]:
        # print('choufuku')
        pass
    else:
        # j+1文字で重複なしの場合(j=0,1,2,3,4)
        s = ''.join(s)
        lens = len(s)
        for i in range(len(listj)):
            num = s.index(''.join(listj[i]))
            a = lens - num
            # print('index:',num)
            # print('ansnum:',ansnum)
            if a < k - ansnum:
                ansnum += a
            else:
                ans = s[num:num + k - ansnum]
                ansnum = k + 1
                break
    if ansnum > k:
        break

#print('ans:',ans)
print(ans)

Fixed submission:
s = list(input())
k = int(input())
subs = []
for i in range(min(k,len(s))):
  for j in range(len(s)-i):
    subs.append(''.join(s[j:j+i+1]))
subs = list(set(subs))
subs.sort()
#print(subs)
print(subs[k-1])

Buggy python submission (verdict: Time Limit Exceeded):
s = list(input())
k = int(input())
ansnum = 0
while(ansnum < k):
    #print(s)
    for j in range(k):
        # listj = []
        # for i in range(len(s)-j):
        #     #print(s[i:i+j+1])
        #     listj.append(s[i:i+j+1])
        listj = [s[i:i+j+1] for i in range(len(s)-j)]
        listj.sort()
        #print('listj:',listj)
        # print('j:',j)
        if len(listj) >= 2 and listj[0] == listj[1]:
            # print('choufuku')
            pass
        else:
            # j+1文字で重複なしの場合(j=0,1,2,3,4)
            s = ''.join(s)
            lens = len(s)
            for i in range(len(listj)):
                num = s.index(''.join(listj[i]))
                a = lens - num
                # print('index:',num)
                # print('ansnum:',ansnum)
                if a < k - ansnum:
                    ansnum += a
                else:
                    ans = s[num:num + k-ansnum]
                    ansnum = k + 1
                    break
        if ansnum > k:
            break

#print('ans:',ans)
print(ans)

Fixed submission:
s = list(input())
k = int(input())
subs = []
for i in range(min(k,len(s))):
  for j in range(len(s)-i):
    subs.append(''.join(s[j:j+i+1]))
subs = list(set(subs))
subs.sort()
#print(subs)
print(subs[k-1])

Buggy python submission (verdict: Time Limit Exceeded):
s = list(input())
k = int(input())
ansnum = 0

while(ansnum < k):
    #print(s)
    for j in range(k):
        listj = []
        for i in range(len(s)-j):
            #print(s[i:i+j+1])
            listj.append(s[i:i+j+1])
        listj.sort()
        # print('listj:',listj)
        # print('j:',j)
        if len(listj) >= 2 and listj[0] == listj[1]:
            # print('choufuku')
            pass
        else:
            # j+1文字で重複なしの場合(j=0,1,2,3,4)
            s = ''.join(s)
            for i in range(len(listj)):
                num = s.index(''.join(listj[i]))
                # print('index:',num)
                # print('ansnum:',ansnum)
                if (len(s) - num) < k - ansnum:
                    ansnum += len(s) - num
                else:
                    ans = s[num:num + k - ansnum]
                    ansnum = k + 1
                    break
        if ansnum > k:
            break

#print('ans:',ans)
print(ans)

Fixed submission:
s = list(input())
k = int(input())
subs = []
for i in range(min(k,len(s))):
  for j in range(len(s)-i):
    subs.append(''.join(s[j:j+i+1]))
subs = list(set(subs))
subs.sort()
#print(subs)
print(subs[k-1])