#include<bits/stdc++.h>
using namespace std;
string s;
int k,a;
int cnt=11;
int main(){
	cin>>s;
	cin>>k;
	int n=s.length();
	a=n-k;
	int ans=-1;
	for(int i=0;i<a;i++){
		cnt=11;
		for(int j=ans+1;j<=k+i;j++){
			if(i==0&&s[j]-'0'==0){
			    continue;
			}
			else if(s[j]-'0'<cnt){
				cnt=s[j]-'0';
				ans=j;
			}
		}
		cout<<char(cnt+'0');
	}
	return 0;
}