#include <iostream>
#include <cstdio>
#include <string>
using namespace std;
//freopen("data.txt","r",stdin);
string s;
int a;
while(cin>>s>>a)
{
string fina;
a=s.length()-a;
if(a==0)
{
cout<<0<<endl;
continue;
}
int which=-1;
while(a>0)
{
int len=s.length();
char cmin=s[which+1];
which++;
for(int i=which+1;i<len-a+1;i++)
{
if(s[i]<cmin)
{
which=i;
cmin=s[i];
}
}
a--;
fina=fina+cmin;
}
while(fina[0]=='0'&&fina.length()>1)fina.erase(fina.begin());
cout<<fina<<endl;
}
return 0;
}