#include<iostream>
#include<cstdio>
#include<string>
#include<cstring>
#include<algorithm>
using namespace std;
int sizes[256],n,k,len,reachedbiggest=0;
char letters[26];
int a[10000];
string sol;

string genstr()
{
     string res;
     for( int i = 0; i < k; i++ )
     {
          res+=letters[a[i]-1];
     }
     return res;
}

bool comp( string str1, string str2 )
{
     for( int i = 0; i < str1.length(); i++ )
     {
          if( sizes[(int)str1[i]] != sizes[(int)str2[i]] )
          {
              if( sizes[(int)str1[i]] > sizes[(int)str2[i]] )
                  return true;
              return false;
          }
     }
     return false;
}

bool checkperm( string str )
{
     if( str.length() < 2 )
         return false;
     for( int i = 1; i < str.length(); i++ )
     {
          string test;
          test = str.substr( i, str.length()-i ) + str.substr( 0, i );
          if( comp( test, str ) == false )
              return false;
     }
     sol = str;
     return true;
}

void CheckString()
{
     if( reachedbiggest == n )
         return;
     if( checkperm(genstr()) )
         reachedbiggest++;
     
}

void var(int p)
{
	if(p == k+1)
	{
        CheckString();
		return;
	}
	for(int i = 1; i <= len; i++)
	{
       a[p-1] = i;
	   var(p+1);
    }
}


int main()
{
    freopen( "nthword.in", "r", stdin );
    freopen( "nthword.out", "w", stdout );
    for( int i = 0; i < 256; i++ )
    {
         sizes[i]=26;
    }
    scanf("%s", letters);
    scanf("%d%d", &k, &n );
    len = strlen(letters);
    for( int i = 0; i < len; i++ )
    {
         sizes[(int)letters[i]]=i;
    }
    var(1);
    printf("%s",sol.c_str());
    return 0;
}