#include <iostream>
#include <fstream>
using namespace std;
typedef long long lld;
struct cool
{
    char sym;
    lld key;
};
lld counter=0,n,k,arr[10002],brb,indw;
cool al[26];
bool end=false;
bool move=false;
lld maxb;
bool flagos=false;
void req(lld ind,lld target)
{
    lld i,j;

    if (end) return;
    if (ind>target) return;
    if (ind==target)
    {
        flagos=false;
        while (arr[ind]<=brb)
        {
            flagos=true;
            counter++;
            /*for (i=1;i<=k;i++)
            {
                cout<<al[arr[i]].sym;
            }
            cout<<endl;*/
            if (counter==n)
            {
                for (i=1;i<=k;i++)
                {
                    cout<<al[arr[i]].sym;
                }
                cout<<endl;
                end=true;
                return ;
            }
            arr[ind]++;
        }
            indw--;
            maxb++;
            for (i=target;i>=indw;i--)
            {
                arr[i]=maxb;
            }
            req(ind,target);
    }
    req(ind+1,target);
}
int main ()
{
    freopen ("nthword.in","r",stdin);
    freopen ("nthword.out","w",stdout);
    lld i,j,t;
    string in;
    cin>>in;
    cin>>k>>n;
    brb=in.length();
    for (i=0;i<in.length();i++)
    {
        al[i+1].key=i+1;
        al[i+1].sym=in[i];
    }
    for (i=1;i<=k;i++)
    {
        arr[i]=1;
    }
    arr[k]=2;
    t=k;
    maxb=1;
    indw=k;
    req(1,t);
    return 0;
}
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