Buggy python submission (verdict: Runtime Error):
# ABC 097 C
S = input()
K = int(input())

cand = []
for l in range(1, K+1):
    for i in range(len(S) - l):
        cand.append(S[i:i+l])

cand = sorted(list(set(cand)))
print(cand[K-1])

Fixed submission:
# ABC 097 C

from collections import defaultdict

S = input()
K = int(input())

alphabet = defaultdict(list)
for i, s in enumerate(S):
    alphabet[s].append(i)

alpha_list = sorted(alphabet.keys())
cand = []
i = 0
while len(cand) < K:
    for j in alphabet[alpha_list[i]]:
        if len(S)-j+1 >= K:
            for l in range(1, K+1):
                cand.append(S[j:j+l])
        else:
            for l in range(1, len(S)-j+1):
                cand.append(S[j:j+l])
    cand = list(set(cand))
    if len(cand) >= K:
        break
    i += 1
cand = sorted(cand)
print(cand[K-1])

Buggy python submission (verdict: Time Limit Exceeded):
from collections import defaultdict

S = input()
K = int(input())

alphabet = defaultdict(list)
for i, s in enumerate(S):
    alphabet[s].append(i)

alpha_list = sorted(alphabet.keys())
cand = []
i = 0
while len(cand) < K:
    for j in alphabet[alpha_list[i]]:
        for l in range(1, len(S)-j+1):
            cand.append(S[j:j+l])
    cand = list(set(cand))
    if len(cand) >= K:
        break
    i += 1
cand = sorted(cand)
print(cand[K-1])

Fixed submission:
# ABC 097 C

from collections import defaultdict

S = input()
K = int(input())

alphabet = defaultdict(list)
for i, s in enumerate(S):
    alphabet[s].append(i)

alpha_list = sorted(alphabet.keys())
cand = []
i = 0
while len(cand) < K:
    for j in alphabet[alpha_list[i]]:
        if len(S)-j+1 >= K:
            for l in range(1, K+1):
                cand.append(S[j:j+l])
        else:
            for l in range(1, len(S)-j+1):
                cand.append(S[j:j+l])
    cand = list(set(cand))
    if len(cand) >= K:
        break
    i += 1
cand = sorted(cand)
print(cand[K-1])

Buggy python submission (verdict: Runtime Error):
from collections import defaultdict

S = input()
K = int(input())

alphabet = defaultdict(list)
for i, s in enumerate(S):
    alphabet[s].append(i)

alpha_list = sorted(alphabet.keys())
cand = []
i = 0
while len(cand) < K:
    for j in alphabet[alpha_list[i]]:
        for l in range(1, len(S)-j+1):
            cand.append(S[j:j+l])
    cand = list(set(cand))
    if len(cand) < K:
        break
    i += 1
cand = sorted(cand)
print(cand[K-1])

Fixed submission:
# ABC 097 C

from collections import defaultdict

S = input()
K = int(input())

alphabet = defaultdict(list)
for i, s in enumerate(S):
    alphabet[s].append(i)

alpha_list = sorted(alphabet.keys())
cand = []
i = 0
while len(cand) < K:
    for j in alphabet[alpha_list[i]]:
        if len(S)-j+1 >= K:
            for l in range(1, K+1):
                cand.append(S[j:j+l])
        else:
            for l in range(1, len(S)-j+1):
                cand.append(S[j:j+l])
    cand = list(set(cand))
    if len(cand) >= K:
        break
    i += 1
cand = sorted(cand)
print(cand[K-1])

Buggy python submission (verdict: Time Limit Exceeded):
from collections import defaultdict

S = input()
K = int(input())

alphabet = defaultdict(list)
for i, s in enumerate(S):
    alphabet[s].append(i)

alpha_list = sorted(alphabet.keys())
cand = []
i = 0
while len(cand) < K:
    for j in alphabet[alpha_list[i]]:
        for l in range(1, len(S)-j+1):
            cand.append(S[j:j+l])
    cand = list(set(cand))
    i += 1
cand = sorted(cand)
print(cand[K-1])

Fixed submission:
# ABC 097 C

from collections import defaultdict

S = input()
K = int(input())

alphabet = defaultdict(list)
for i, s in enumerate(S):
    alphabet[s].append(i)

alpha_list = sorted(alphabet.keys())
cand = []
i = 0
while len(cand) < K:
    for j in alphabet[alpha_list[i]]:
        if len(S)-j+1 >= K:
            for l in range(1, K+1):
                cand.append(S[j:j+l])
        else:
            for l in range(1, len(S)-j+1):
                cand.append(S[j:j+l])
    cand = list(set(cand))
    if len(cand) >= K:
        break
    i += 1
cand = sorted(cand)
print(cand[K-1])

Buggy python submission (verdict: Runtime Error):
from collections import defaultdict

S = input()
K = int(input())

alphabet = defaultdict(list)
for i, s in enumerate(S):
    alphabet[s].append(i)

alpha_list = sorted(alphabet.keys())
cand = []
i = 0
while len(cand) < K:
    for j in alphabet[alpha_list[i]]:
        for l in range(1, len(S)-j+1):
            cand.append(S[j:j+l])
    i += 1
cand = sorted(list(set(cand)))
print(cand[K-1])

Fixed submission:
# ABC 097 C

from collections import defaultdict

S = input()
K = int(input())

alphabet = defaultdict(list)
for i, s in enumerate(S):
    alphabet[s].append(i)

alpha_list = sorted(alphabet.keys())
cand = []
i = 0
while len(cand) < K:
    for j in alphabet[alpha_list[i]]:
        if len(S)-j+1 >= K:
            for l in range(1, K+1):
                cand.append(S[j:j+l])
        else:
            for l in range(1, len(S)-j+1):
                cand.append(S[j:j+l])
    cand = list(set(cand))
    if len(cand) >= K:
        break
    i += 1
cand = sorted(cand)
print(cand[K-1])