#include<iostream>
#include<stdio.h>
#include<string.h>

using namespace std;

char alphabet[26];
int letters[10000];
int n,k;
int len;


void init()
{
	FILE *pFile = fopen("nthword.in","r");
	fgets(alphabet,25,pFile);
	len = strlen(alphabet);
	fscanf(pFile,"%d%d",&k,&n);
	fclose(pFile);
}

void printString();

void buildArray()
{
	for (int i = 0; i < n; i++)
	{
		for (int j = k-1; j >= 0; j--)
		{
			if (letters[j] < len-2){
				letters[j]++;
				for (int l = j+1; l < k; l++)
				{
					letters[l] = letters[j];
				}
				break;
			}
		}
	}
}

void printString()
{
	FILE *pFile = fopen("nthword.out","w");
	for (int i = 0; i < k; i++)
	{
		fprintf(pFile,"%c",alphabet[letters[i]]);
	}
	fclose(pFile);
}

int main()
{
	init();
	buildArray();
	printString();
	//printf("%c",alphabet[letters[0]]);
}<!-- 0.0539s -->