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#include<bits/stdc++.h>
#define ll long long
#define ull unsigned long long
#define ui unsigned int
#define inf 1000000000
#define INF 1000000000000000000LL
#define VI vector<int>
#define VLL vector<ll>
#define PII pair<int, int>
#define st first
#define nd second
#define pb push_back
#define mp make_pair
#define mt make_tuple
#define eb emplace_back
#define endl '\n'
#define REP(x, y) for(int x = 0; x < (y); ++x)
#define FOR(x, y, z) for(int x = y; x <= (z); ++x)
using namespace std;

ll n, k, a, l = -1;

string s;

ll ile(ll d)
{
	++d;

	if(d>59)
		return INF+7;

	return (1ll<<d)-1;
}

string res;

int main()
{
	ios_base::sync_with_stdio(0);
	cin.tie(NULL);

	cin >> n >> k;

	for(int i = 1; i <= n && k; ++i)
	{
		a = 1;

		while(a<3 && (a==l || ile(n-i)<k))
		{
			if(a==l)
			{
				++a;
				continue;
			}

			k -= ile(n-i);
			++a;
		} 

		s += char(a+96);

		if(a==l)
		{
			cout << "NIE";
			return 0;
		}

		l = a;

		--k;	
	}

	if(k)
		cout << "NIE";
	else
		cout << s;
}