#include <stdio.h>
#include <stdlib.h>
int hash(int N)
{
  int work = N;
  int hash = 0;
  int base = 10;
  while (1) {
    while (work != 0) {
      hash += (work % base);
      work /= base;
    }
    if (hash >= base) {
      work = hash;
      hash = 0;
    } else {
      break;
    }
  }
  return hash;
}
int Pr_begin = 0;
int Pr_end = 0;
int *Pr = 0;
int pr_gen(int K, int N)
{
  int i, j;
  char *chk = (char*)malloc(sizeof(char)*(N+1));
  for (i=0; i<=N; i++) chk[i] = 1;
  chk[0] = 0;
  chk[1] = 0;
  for (i=2; i<=N; i++) {
    if (chk[i] == 1) {
      for (j=i*2; j<=N; j+=i) chk[j] = 0;
      Pr_end++;
    }
  }
  Pr = (int*)malloc(sizeof(int)*Pr_end);
  Pr_end = 0;
  for (i=0; i<=N; i++) {
    if (chk[i] == 1) {
      Pr[Pr_end] = i;
      Pr_end++;
    }
  }
  free(chk);
  chk = 0;

  if (K <= Pr[0]) {
    Pr_begin = 0;
  } else {
    for (i=0; i<Pr_end-1; i++) {
      if ((Pr[i] < K)&&(K <= Pr[i+1])) break;
    }
    Pr_begin = i+1;
  }
  return 0;
}
int main()
{
  int K;
  int N;
  scanf("%d", &K);
  scanf("%d", &N);

  pr_gen(K, N);

  int i;
  int pr_n = Pr_end - Pr_begin;
  int *key = (int*)malloc(sizeof(int)*pr_n);
  for (i=0; i<pr_n; i++) key[i] = hash(Pr[Pr_begin + i]);

  int *count = (int*)malloc(sizeof(int)*pr_n);
  for (i=0; i<pr_n; i++) count[i] = 0;
  int begin;
  int end;
  int match = 0;
  for (begin = 0; begin < pr_n-1; ) {
    for (end = begin+1; end < pr_n; end++) {
      for (i=begin; i<end; i++) {
        if (key[i] == key[end]) {
          match = 1;
          goto BRK;
        }
      }
    }
    BRK:
    count[begin] = end - begin;
    if (match == 1) {
      begin = i+1;
      match = 0;
    } else {
      break;
    }
  }
  count[pr_n-1] = 1;

  int max = 0;
  int pr_i;
  for (i=0; i<pr_n; i++) {
    if (max <= count[i]) {
      max = count[i];
      pr_i = i;
    }
  }
  printf("%d\n", Pr[Pr_begin + pr_i]);
  return 0;
}