package no371;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Scanner;

public class Main {

	public static ArrayList<Integer> primes = primeList(100000);
	
	//参考 http://kmjp.hatenablog.jp/entry/2016/05/14/0900
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long l = sc.nextLong();
		long h = sc.nextLong();
		System.out.println(solve(l,h));
	}
	
	public static long solve(long l,long h) {
		for(int i=primes.size()-1;i>=0;i--) {
			long p = primes.get(i);
			if (p * p > h) continue;
			
			for(long x = h / p * p; x >= l; x -= p) {
				boolean flag = true;
				for(long q:primes) {
					if (q >= p) break;
					if (x % q == 0) {
						flag = false;
						break;
					}
				}
				if (flag) {
					return x;
				}
			}
		}
		
		return -1; //???
	}

	public static boolean[] isPrimeArray(int max) {
		boolean[] isPrime = new boolean[max+1];
		Arrays.fill(isPrime, true);
		isPrime[0] = isPrime[1] = false;
		for(int i=2;i*i<=max;i++) {
			if (isPrime[i]) {
				int j = i * 2;
				while(j<=max) {
					isPrime[j] = false;
					j += i;
				}
			}
		}
		return isPrime;
	}
	public static ArrayList<Integer> primeList(int max) {
		boolean[] isPrime = isPrimeArray(max);
		ArrayList<Integer> primeList = new ArrayList<Integer>();
		for(int i=2;i<=max;i++) {
			if (isPrime[i]) {
				primeList.add(i);
			}
		}
		return primeList;
	}
	
	public static ArrayList<Long> primeFactorL(ArrayList<Integer> primeList,long num) {
		ArrayList<Long> ret = new ArrayList<Long>();
		for(int p:primeList) {
			while(num % p == 0) {
				num /= p;
				ret.add((long) p);
			}
		}
		if (num > 1) {
			ret.add(num);
		}
		return ret;
	}
}