#include<iostream>

#include<cstdio>

#include<cstring>

#include<cmath>

using namespace std;

char a[],ans[];

int dp[][];

int Min(int x,int y)

{

    return a[x] <= a[y] ? x : y;

}

void rmq_init(int len)

{

    for(int i = ;i < len;i++)  dp[i][] = i;

    for(int j = ;(<<j) < len;j++)

    {

        for(int i = ;i+(<<j)- < len;i++)

        {

            dp[i][j] = Min(dp[i][j-],dp[i+(<<(j-))][j-]);

        }

    }

}

int rmq_query(int l,int r)

{

    int k = (int)(log((double)(r-l+))/log(2.0));

    return Min(dp[l][k],dp[r-(<<k)+][k]);

}

int main()

{

    int n,i;

    while(~scanf("%s%d",a,&n))

    {

        int len = strlen(a);

        rmq_init(len);

        n = len-n;

        int pos = ,num = ;

        while(n)

        {

            pos = rmq_query(pos,len-n);

            ans[num++] = a[pos++];

            n--;

        }

        for(i = ;i < num && ans[i] == '';i++);

        if(i == num)    printf("0\n");

        else

        {

            for(;i < num;i++)   printf("%c",ans[i]);

            printf("\n");

        }

    }

    return ;

}