Buggy python submission (verdict: Runtime Error):
s = input()
K = int(input())
L = len(s)
cand = []

if L > 5:
    c = []
    order = sorted(list(s))
    for i in range(L):
        if order[i] in c:
            pass
        else:
            c.append(order[i])
            if len(c) == 3: #5:
                break
else:
    c = list(s)

for i in range(L):
    if s[i] in c:
        for j in range(i+1,min(i+K+1,L+1)):
            cand.append(s[i:j])
cand.sort()

i = 0
if len(cand) == 1:
    print(cand[0])
    exit()
while True:
    if cand[i] == cand[i+1]:
        i+=1
        continue
    K-=1
    i+=1
    if K == 0:
        print(cand[i-1])
        break


Fixed submission:
s = input()
K = int(input())
L = len(s)
cand = []

if L > 5:
    c = []
    order = sorted(list(s))
    for i in range(L):
        if order[i] in c:
            pass
        else:
            c.append(order[i])
            if len(c) == 5:
                break
else:
    c = list(s)

for i in range(L):
    if s[i] in c:
        for j in range(i+1,min(i+K+1,L+1)):
            cand.append(s[i:j])
cand.sort()

i = 0
if len(cand) == 1:
    print(cand[0])
    exit()

i = 0
while True:
    K -= 1
    if K == 0:
        print(cand[i])
        break
    i += 1
    while(cand[i] == cand[i-1]):
        cand.pop(i)

Buggy python submission (verdict: Runtime Error):
s = input()
K = int(input())
L = len(s)
cand = []

if L > 5:
    c = []
    order = sorted(list(s))
    for i in range(L):
        if order[i] in c:
            pass
        else:
            c.append(order[i])
            if len(c) == 3; #5:
                break
else:
    c = list(s)

for i in range(L):
    if s[i] in c:
        for j in range(i+1,min(i+K+1,L+1)):
            cand.append(s[i:j])
cand.sort()

i = 0
if len(cand) == 1:
    print(cand[0])
    exit()
while True:
    if cand[i] == cand[i+1]:
        i+=1
        continue
    K-=1
    i+=1
    if K == 0:
        print(cand[i-1])
        break


Fixed submission:
s = input()
K = int(input())
L = len(s)
cand = []

if L > 5:
    c = []
    order = sorted(list(s))
    for i in range(L):
        if order[i] in c:
            pass
        else:
            c.append(order[i])
            if len(c) == 5:
                break
else:
    c = list(s)

for i in range(L):
    if s[i] in c:
        for j in range(i+1,min(i+K+1,L+1)):
            cand.append(s[i:j])
cand.sort()

i = 0
if len(cand) == 1:
    print(cand[0])
    exit()

i = 0
while True:
    K -= 1
    if K == 0:
        print(cand[i])
        break
    i += 1
    while(cand[i] == cand[i-1]):
        cand.pop(i)

Buggy python submission (verdict: Runtime Error):
s = input()
K = int(input())
L = len(s)
cand = []

if L > 5:
    c = []
    order = sorted(list(s))
    for i in range(L):
        if order[i] in c:
            pass
        else:
            c.append(order[i])
            if len(c) == 5:
                break
else:
    c = list(s)

for i in range(L):
    if s[i] in c:
        for j in range(i+1,min(i+K+1,L+1)):
            cand.append(s[i:j])
cand.sort()

i = 0
if len(cand) == 1:
    print(cand[0])
    exit()
while True:
    if cand[i] == cand[i+1]:
        i+=1
        continue
    K-=1
    i+=1
    if K == 0:
        print(cand[i-1])
        break


Fixed submission:
s = input()
K = int(input())
L = len(s)
cand = []

if L > 5:
    c = []
    order = sorted(list(s))
    for i in range(L):
        if order[i] in c:
            pass
        else:
            c.append(order[i])
            if len(c) == 5:
                break
else:
    c = list(s)

for i in range(L):
    if s[i] in c:
        for j in range(i+1,min(i+K+1,L+1)):
            cand.append(s[i:j])
cand.sort()

i = 0
if len(cand) == 1:
    print(cand[0])
    exit()

i = 0
while True:
    K -= 1
    if K == 0:
        print(cand[i])
        break
    i += 1
    while(cand[i] == cand[i-1]):
        cand.pop(i)

Buggy python submission (verdict: Runtime Error):
s = input()
K = int(input())
L = len(s)
cand = []
for i in range(L):
    for j in range(i+1,min(i+K+1,L+1)):
        cand.append(s[i:j])
cand.sort()

i = 0
if len(cand) == 1:
    print(cand[0])
    exit()
while True:
    if cand[i] == cand[i+1]:
        i+=1
        continue
    K-=1
    i+=1
    if K == 0:
        print(cand[i-1])
        break


Fixed submission:
s = input()
K = int(input())
L = len(s)
cand = []

if L > 5:
    c = []
    order = sorted(list(s))
    for i in range(L):
        if order[i] in c:
            pass
        else:
            c.append(order[i])
            if len(c) == 5:
                break
else:
    c = list(s)

for i in range(L):
    if s[i] in c:
        for j in range(i+1,min(i+K+1,L+1)):
            cand.append(s[i:j])
cand.sort()

i = 0
if len(cand) == 1:
    print(cand[0])
    exit()

i = 0
while True:
    K -= 1
    if K == 0:
        print(cand[i])
        break
    i += 1
    while(cand[i] == cand[i-1]):
        cand.pop(i)