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#include <iostream>
#include <limits>
#include <string>
using namespace std;

namespace {

constexpr auto inf = numeric_limits<long long>::max();

long long pow2(int n)
{
  if (n >= 63) return inf;
  return 1LL << n;
}

bool solve(string& res, int n, long long k, char last='\0')
{
  if (k == 0) return true;
  if (n == 0) return false;
  --k;
  auto cnt = pow2(n) - 1;
  for (char c: {'a', 'b', 'c'}) {
    if (c == last) continue;
    if (k < cnt) {
      res.push_back(c);
      return solve(res, n-1, k, c);
    }
    k -= cnt;
  }
  return false;
}

}

int main()
{
  iostream::sync_with_stdio(false);
  cin.tie(nullptr);

  int n;
  long long k;
  cin >> n >> k;

  string res;
  if (solve(res, n, k)) cout << res << '\n';
  else cout << "NIE\n";

  return 0;
}