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import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.List;

public class slo {
	
	public static char[] L = {'a', 'b', 'c'};

	public static void main(String[] args) {
		long n = R.l();
		long k = R.l();

    	long x = (long) Math.pow(2, n > 60 ? 60 : n) - 1;
    	int p = 3;
    	if (k > 3 * x) {
    		System.out.println("NIE");
    	} else {
	    	while (k > 0) {
	    		k--;
	    		p = (int) (k / x) >= p ? (int) (k / x + 1) : (int) (k / x);
	    		W.c(L[p]);
	    		k = k % x;
	    		n--;
            	x = (long) Math.pow(2, n > 60 ? 60 : n) - 1;
	    	}
    	}
		W.flush();
	}
	
    public static void go(long n, long k) {
     }

	static class R {
		static InputStream is=new BufferedInputStream(System.in);
		static int b='\n';
		static void next(){try{b=is.read();}catch(Exception e){}}
		static void skip(){while(b=='\n'||b==' '||b=='\r'||b=='\t')next();}
		static char c(){skip();char c=(char)b;next();return c;}
		static int i(){skip();int i=0;while(b>='0'&&b<='9'){i=10*i+(b-'0');next();}return i;}
		static long l(){skip();long i=0;while(b>='0'&&b<='9'){i=10*i+(b-'0');next();}return i;}
	}
	static class W {
		static OutputStream os=new BufferedOutputStream(System.out,4096);
		static void b(int b){try{os.write(b);}catch(Exception e){}}
		static void c(char c){b(c);}
		static void cs(char c){c(c);space();}
		static void cn(char c){c(c);newLine();}
		static void i(int i){if(i>9)i(i/10);b('0'+(i%10));}
		static void is(int i){i(i);space();}
		static void in(int i){i(i);newLine();}
		static void l(long l){if(l>9)l(l/10);b('0'+(int)(l%10));}
		static void ls(int l){l(l);space();}
		static void ln(int l){l(l);newLine();}
		static void s(String s){try{os.write(s.getBytes());}catch(Exception e){}}
		static void ss(String s){s(s);space();}
		static void sn(String s){s(s);newLine();}
		static void tn(boolean b){sn(b?"TAK":"NIE");}
		static void space(){b(' ');}
		static void newLine(){b('\n');}
		static void flush(){try{os.flush();}catch(Exception e){}};
	}

}