#include <iostream>

using namespace std;

int main() {
	int k=0, p=0, n=0, i=0;
	cin >> k;
	cin >> p;
	for (i = 9999; i >= 0; i--) {
		bool prime = true;
		for (int j = 2; j < i; j++) {
			if (i % j == 0) {
				prime = false;
			}
		}
		bool containsForbiddenNumber = false;
		if (prime) {
			int c = i;
			while (c > 0) {
				if (c % 10 == k || c % 10 == p) {
					containsForbiddenNumber = true;
					break;
				}
				c = c / 10;
			}
		}
		if (prime && !containsForbiddenNumber) {
			n = i;
			break;
		}
	}
	cout << n;
	return 0;
}