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import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.StringTokenizer;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class slo {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        Slowo solver = new Slowo();
        solver.solve(1, in, out);
        out.close();
    }

    static class Slowo {
        public void solve(int testNumber, InputReader in, PrintWriter out) {
            int N = in.nextInt();
            long K = in.nextLong();
            long INF = Long.MAX_VALUE;
            long MAX = (long) 1e18;
            long ways[] = new long[N + 1];
            for (int i = 1; i <= N; i++) {
                ways[i] = Math.min(2L * ways[i - 1] + 1, MAX);
            }
            long ALL = 3L * ways[N];

            if (ALL < K) {
                out.println("NIE");
            } else {
                char ANS[] = new char[N];
                char last = 0;
                for (int i = N; i >= 1; i--) {
                    char[] nxt = next(last);
                    for (int j = 0; j < nxt.length && K > 0; j++) {
                        if (K > ways[i]) {
                            K -= ways[i];
                        } else {
                            ANS[N - i] += nxt[j];
                            last = nxt[j];
                            K--;
                            break;
                        }
                    }
                }
                out.println(new String(ANS).trim());
            }
        }

        private char[] next(char last) {
            switch (last) {
                case 0:
                    return new char[]{'a', 'b', 'c'};
                case 'a':
                    return new char[]{'b', 'c'};
                case 'b':
                    return new char[]{'a', 'c'};
                case 'c':
                    return new char[]{'a', 'b'};
            }
            throw new IllegalStateException();
        }

    }

    static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }

        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

        public long nextLong() {
            return Long.parseLong(next());
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

    }
}