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#include <iostream>
#include <cmath>
#include <sstream>

using namespace std;

stringstream out;

char characters[] = { 'a', 'b', 'c' };

void getNextCharacter(int &previous, int number)
{
	if (previous == 0)
	{
		if (number == 0)
		{
			out << 'b';
			previous = 1;
		}
		else
		{
			out << 'c';
			previous = 2;
		}
	}
	else if (previous == 1)
	{
		if (number == 0)
		{
			out << 'a';
			previous = 0;
		}
		else
		{
			out << 'c';
			previous = 2;
		}
	}
	else if (previous == 2)
	{
		if (number == 0)
		{
			out << 'a';
			previous = 0;
		}
		else
		{
			out << 'b';
			previous = 1;
		}
	}
	else
	{
		if (number == 0)
			out << 'a';
		else if (number == 1)
			out << 'b';
		else
			out << 'c';
		previous = number;
	}
}

int main()
{
	ios_base::sync_with_stdio(false);
	long long n, k;
	int previous = -1;
	cin >> n >> k;
	k--;
	for (int i = n; i > 0; i--)
	{
		if (i > 60)
		{
			getNextCharacter(previous, 0);
			k--;
			if (k < 0)
				break;
		}
		else
		{
			long long divisor = (1LL << i) - 1;
			long long modulo = k % divisor;
			k /= divisor;
			if (k > 2)
			{
				out.clear();
				out << "NIE";
				break;
			}
			getNextCharacter(previous, k);
			k = modulo - 1;
			if (k < 0)
				break;
		}
	}


	cout << out.str() << endl;
	return 0;
}