#include<bits/stdc++.h>
using namespace std;
using LL=long long;
using ULL=unsigned long long;
#define rep(i,n) for(int i=0; i<(n); i++)

const ULL Z = 5000000;
bool sieve[Z + 1];
ULL bull[Z + 1]; ULL offset;

int main() {
	ULL L, R; cin >> L >> R;
	offset = max(Z, R) - Z;
	rep(i, Z + 1) bull[i] = i;

	sieve[0] = sieve[1] = true;
	for (ULL i = 2; i < Z; i++) {
		if (sieve[i]) continue;
		if (i <= 1000) for (ULL j = i * i; j < Z; j += i) sieve[j] = true;
		for (ULL j = i - (offset + i - 1) % i - 1; j <= Z; j += i) bull[j] = min(bull[j], i);
	}

	ULL ans = 0, val = 0;
	for (ULL i = max(offset, L) - offset; i <= R - offset; i++)
		if (bull[i] != i) if (val <= bull[i]) {
			val = bull[i]; ans = offset + i;
		}
	cout << ans << endl;

	return 0;
}