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// potyczki.cpp : Defines the entry point for the console application.
//


#include <iostream>
#include <cstring>
#include <cstdlib>
#include <list>
#include <math.h>

using namespace std;



char get_next_letter(char last, int firstSecondThird)
{
	if (last == 'a')
	{
		if (firstSecondThird == 1) return 'b';
		if (firstSecondThird == 2) return 'c';
		if (firstSecondThird == 3)
			return 'd';
	}
	if (last == 'b')
	{
		if (firstSecondThird == 1) return 'a';
		if (firstSecondThird == 2) return 'c';
		if (firstSecondThird == 3)
			return 'd';
	}
	if (last == 'c')
	{
		if (firstSecondThird == 1) return 'a';
		if (firstSecondThird == 2) return 'b';
		if (firstSecondThird == 3)
			return 'd';
	}
	if (last == 'd')
	{
		if (firstSecondThird == 1) return 'a';
		if (firstSecondThird == 2) return 'b';
		if (firstSecondThird == 3) return 'c';
	}
}


long long liczbamozliwychwyrazow(long long len, char last)
{
	int mnoznik = 2;
	if (last == 'd') mnoznik = 3;
	return mnoznik * (pow(2, len) - 1);
}
long long liczbamozliwychpodwyrazow(long long len)
{
	return pow(2, len)-1 ;
}

void nextletter(char last, long long n, long long k)
{
	if (k == 0)
	{
		return;
	}

	
	long long aa = liczbamozliwychpodwyrazow(n);
	
		int firSecThird = 1;
		while (k > aa)
		{
			k -= aa;
			firSecThird++;
		}
		n--;
		k--;
		last = get_next_letter(last, firSecThird);
		cout << last;
		nextletter(last, n, k);

	
}


	
int main()
{
	long long n = 1;
	long long k = 1;
	cin >> n >> k;
	char last = 'd';
	if ((n < 63) && (liczbamozliwychwyrazow(n, 'd') < k))
	{
		cout << "NIE";
		return 0;
	}
	while (n > 62)
	{
		n--;
		k--;
		last = get_next_letter(last, 1);
		cout << last;
		if (k == 0)
			return 0;
	}

	nextletter(last, n, k);
	char aar[100];
	cin >> aar;
	return 0;
}