// yukicoder: 6. 使いものにならないハッシュ
// 2021.8.13

#include <stdio.h>
#include <math.h>

#define MAX  200005
char cn[MAX] = { 1,1,0,0,1 };			// 合成数
int  a[MAX], hash[MAX], sz;

void sieve(int max) {
	int i, j;
	int sq = sqrt(max);
//	for (i = 2; i <= max; i+=2) cn[i] = 1;
	for (i = 3; i <= sq; i += 2) if (!cn[i]) {
		for (j = i*i; j <= max; j += i) cn[j] = 1;
	}
}

int main()
{
	int i, k, t, K, N;
	int ans, w;

	scanf("%d%d", &K, &N);
	sieve(N);
	if (K <= 2) a[0] = hash[0] = 2, sz = 1, i = 3;
	else i = (K/2)*2+1;
	for ( ; i <= N; i+=2) if (!cn[i]) {
		a[sz] = i;
		k = i; while (k >= 10) {
			t = 0; while (k) t += k % 10, k /= 10;
			k = t;
		}
		hash[sz++] = k;
	}

	w = 0; for (i = 0; i < sz; ++i) {
		t = 1<<hash[i];
		k = i+1; while (k < sz && !(t & (1<<hash[k]))) t |= 1<<hash[k++];
		if (k-i+1 >= w) w = k-i+1, ans = a[i];
	}
	printf("%d\n", ans);
	return 0;
}