#include <cstdio>
#include <stdio.h>
#include <stdbool.h>
#include <iostream>
#include <map>
#include <vector>
#include <climits>
#include <stack>
#include <string>
#include <queue>
#include <algorithm>
#include <set>
#include <unordered_set>
#include <unordered_map>
#include <cmath>
#include <cctype>
#include <bitset>
#include <iomanip>
#include <cstring>
#include <numeric>
#include <cassert>
#include <random>
#include <chrono>
#include <fstream>
using namespace std;
#define int long long
#define pii pair<int, int>
#define mp make_pair
#define pb push_back
#define fi first
#define se second
bool prime(int a){
	if (a<2)return 0;
	for (int i=2; i<=sqrt(a); ++i)if (!(a%i))return 0;
	return 1;
}
int32_t main(){
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	int l, r;
	cin>>l>>r;
	if (abs(l-r)<=2){
		cout<<"2\n"<<l<<" "<<r;
		return 0;
	}
	bool die=0;
	vector<int> ans;
	if (l>2){
		if (prime(l-2))ans.pb(l);
		else if (prime(l+2))ans.pb(l), ans.pb(l+2);
		else die=1;
	}
	ans.pb(2);
	if (r>2){
		if (prime(r-2))ans.pb(r);
		else if (prime(r+2))ans.pb(r+2), ans.pb(r);
		else die=1;
	}
	if (die){
		cout<<-1;
		return 0;
	}
	cout<<ans.size()<<"\n";
	for (auto a:ans)cout<<a<<" ";
}
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