import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.lang.management.ManagementFactory; import java.util.ArrayList; import java.util.Arrays; import java.util.HashSet; import java.util.LinkedHashSet; import java.util.List; import java.util.Set; import java.util.function.IntFunction; class Main{ boolean isDebug = ManagementFactory.getRuntimeMXBean().getInputArguments().toString() .contains("-agentlib:jdwp"); final MyReader in = new MyReader(System.in); final MyWriter out = new MyWriter(System.out); public static void main(final String[] args){ new Main().exe(); } private void exe(){ input(); preCalc(); solve(); out.flush(); } int K = in.it(); int N = in.it(); private void input(){} private void preCalc(){} void solve(){ List list = new ArrayList<>(); for (var p:primes(N)) if (K <= p) list.add(new int[] { p, hash(p) }); int ans = 0; int max = 0; Set set = new HashSet<>(); set.add(list.get(0)[1]); for (int i = 0,j = 0;i < list.size();i++) { var s = list.get(i); while (j +1 < list.size() && !set.contains(list.get(j +1)[1])) { set.add(list.get(j +1)[1]); j++; } if (max <= j -i) { ans = s[0]; max = j -i; } set.remove(s[1]); } out.println(ans); } private int hash(int p){ int ret = 0; while (0 < p) { ret += p %10; p /= 10; } return 9 < ret ? hash(ret) : ret; } Set primes(final int bound){ Set ret = new LinkedHashSet<>(); for (int i = 2;i <= bound;i++) { boolean flg = true; for (final int p:ret) if (i %p == 0) { flg = false; break; } else if (i < p *p) break; if (flg) ret.add(i); } return ret; } /* 定数 */ final int mod = 998244353; final String yes = "Yes"; final String no = "No"; /* 入力 */ static class MyReader{ byte[] buf = new byte[1 <<16]; int head = 0; int tail = 0; InputStream in; public MyReader(final InputStream in){ this.in = in; } byte read(){ if (head == tail) { try { tail = in.read(buf); } catch (IOException e) { e.printStackTrace(); } head = 0; } return buf[head++]; } boolean isPrintable(final byte c){ return 32 < c && c < 127; } boolean isNum(final byte c){ return 47 < c && c < 58; } byte nextPrintable(){ byte ret = read(); return isPrintable(ret) ? ret : nextPrintable(); } int it(){ return (int) lg(); } int[] it(final int N){ int[] a = new int[N]; Arrays.setAll(a,i -> it()); return a; } int[][] it(final int H,final int W){ return arr(new int[H][],i -> it(W)); } int idx(){ return it() -1; } int[] idx(final int N){ int[] a = new int[N]; Arrays.setAll(a,i -> idx()); return a; } int[][] idx(final int H,final int W){ return arr(new int[H][],i -> idx(W)); } long lg(){ byte i = nextPrintable(); boolean negative = i == 45; long n = negative ? 0 : i -'0'; while (isPrintable(i = read())) n = 10 *n +i -'0'; return negative ? -n : n; } long[] lg(final int N){ long[] a = new long[N]; Arrays.setAll(a,i -> lg()); return a; } long[][] lg(final int H,final int W){ return arr(new long[H][],i -> lg(W)); } char[] ch(){ return str().toCharArray(); } char[][] ch(final int H){ return arr(new char[H][],i -> ch()); } String line(){ StringBuilder sb = new StringBuilder(); byte c; while (isPrintable(c = read()) || c == ' ') sb.append((char) c); return sb.toString(); } String str(){ StringBuilder sb = new StringBuilder(); sb.append((char) nextPrintable()); byte c; while (isPrintable(c = read())) sb.append((char) c); return sb.toString(); } String[] str(final int N){ return arr(new String[N],i -> str()); } T[] arr(final T[] arr,final IntFunction f){ Arrays.setAll(arr,f); return arr; } } /* 出力 */ static class MyWriter{ OutputStream out; byte[] buf = new byte[1 <<16]; byte[] ibuf = new byte[20]; int tail = 0; public MyWriter(final OutputStream out){ this.out = out; } void flush(){ try { out.write(buf,0,tail); tail = 0; } catch (IOException e) { e.printStackTrace(); } } void write(final byte b){ buf[tail++] = b; if (tail == buf.length) flush(); } void write(final byte[] b,final int off,final int len){ for (int i = off;i < off +len;i++) write(b[i]); } void write(final char c){ write((byte) c); } void write(long n){ if (n < 0) { n = -n; write('-'); } int i = ibuf.length; do { ibuf[--i] = (byte) (n %10 +'0'); n /= 10; } while (n > 0); write(ibuf,i,ibuf.length -i); } void println(final long n){ write(n); write('\n'); } public void println(final double d){ println(String.valueOf(d)); } void println(final String s){ byte[] b = s.getBytes(); for (byte bb:b) write(bb); write('\n'); } public void println(final char[] s){ for (char bb:s) write(bb); write('\n'); } void println(final int[] a){ for (int i = 0;i < a.length;i++) { if (0 < i) write(' '); write(a[i]); } write('\n'); } } }