import java.io.OutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.io.BufferedWriter; import java.io.IOException; import java.io.InputStreamReader; import java.io.UncheckedIOException; import java.nio.charset.Charset; import java.util.StringTokenizer; import java.io.Writer; import java.io.OutputStreamWriter; import java.io.BufferedReader; import java.io.InputStream; /** * Built using CHelper plug-in * Actual solution is at the top * * @author mikit */ public class Main { public static void main(String[] args) { InputStream inputStream = System.in; OutputStream outputStream = System.out; LightScanner in = new LightScanner(inputStream); LightWriter out = new LightWriter(outputStream); PowerOfTwo solver = new PowerOfTwo(); solver.solve(1, in, out); out.close(); } static class PowerOfTwo { public void solve(int testNumber, LightScanner in, LightWriter out) { // out.setBoolLabel(LightWriter.BoolLabel.YES_NO_FIRST_UP); int n = in.ints() - in.ints(); out.ans(n < 0 ? 0 : 1 << n).ln(); } } static class LightWriter implements AutoCloseable { private final Writer out; private boolean autoflush = false; private boolean breaked = true; public LightWriter(Writer out) { this.out = out; } public LightWriter(OutputStream out) { this(new BufferedWriter(new OutputStreamWriter(out, Charset.defaultCharset()))); } public LightWriter print(char c) { try { out.write(c); breaked = false; } catch (IOException ex) { throw new UncheckedIOException(ex); } return this; } public LightWriter print(String s) { try { out.write(s, 0, s.length()); breaked = false; } catch (IOException ex) { throw new UncheckedIOException(ex); } return this; } public LightWriter ans(String s) { if (!breaked) { print(' '); } return print(s); } public LightWriter ans(int i) { return ans(Integer.toString(i)); } public LightWriter ln() { print(System.lineSeparator()); breaked = true; if (autoflush) { try { out.flush(); } catch (IOException ex) { throw new UncheckedIOException(ex); } } return this; } public void close() { try { out.close(); } catch (IOException ex) { throw new UncheckedIOException(ex); } } } static class LightScanner { private BufferedReader reader = null; private StringTokenizer tokenizer = null; public LightScanner(InputStream in) { reader = new BufferedReader(new InputStreamReader(in)); } public String string() { if (tokenizer == null || !tokenizer.hasMoreTokens()) { try { tokenizer = new StringTokenizer(reader.readLine()); } catch (IOException e) { throw new UncheckedIOException(e); } } return tokenizer.nextToken(); } public int ints() { return Integer.parseInt(string()); } } }