#include<iostream>
#include<cstdio>
#include<cmath>
#include<algorithm>
#include<vector>
#define x first
#define y second
#define endl '\n'
const int N = 200010;
using namespace std;
typedef long long ll;
ll f(ll x) {
	ll t = 1;
	while (t <= x)t <<= 1;
	t >>= 1;
	return t;
}
int main() {
	ll l, r;
	vector<pair<ll, ll>>ans;
	cin >> l >> r;
	if (l == 0) {//如果是左端点的话，则j=0
		l = f(r);//计算小于等于r的最大次幂
		ans.push_back({ 0,r });
	}
	for (ll i = l; i != r;) {
		ll lb = i & -i;//计算lowbit
		ll t = lb * (i / lb + 1);
		if (t <= r)ans.push_back({ i,t });
		else {
			while (lb * (i / lb + 1) > r)lb /= 2;//如果超出范围，减小lb直至不超出范围为止
			t = lb * (i / lb + 1);
			ans.push_back({ i,t });
		}
		i = t;
	}
	cout << ans.size() << '\n';
	for (auto t : ans) {
		cout << t.x << " " << t.y << '\n';
	}
	return 0;
}