s=input()
def check(s):
    res=''
    for i in s:
        if i!=' ':
            res+=i
    return res
s=check(s)
k=int(check(input()))
a=0
index=0
ans=''
k=len(s)-k
for i in range(1,k+1):
    minn=10
    for j in range(a,len(s)-k+i):
       if int(s[j])<minn:
           minn=int(s[j])
           index=j
    ans+=s[index]
    a=index+1
print(int(ans))

样例能过，自己测试正常，洛谷在线IDE也正常 根本不知道怎么错的:(