#include<bits/stdc++.h>
#define int long long
using namespace std;
#define MAX_SIZE 8888
queue<pair<int, int>> q;
vector<pair<int, int>> ans;
bool cmp(pair<int, int> a, pair<int, int> b){
	return a.first < b.first;
}
signed main(){
	int n, m;
	cin >> n >> m;
	q.push({n, m});
	while(!q.empty()){
		int x = q.front().first;
		int y = q.front().second;
		q.pop();
		if (x <= (y - x)){
			q.push({x, (x + y) / 2});
			q.push({(x + y) / 2 + 1, y});
		} else {
			ans.push_back({x, y});
		}
	}
	sort(ans.begin(), ans.end(), cmp);
	cout << ans.size() << "\n";
	for (auto it = ans.begin(); it != ans.end(); it++){
		cout << it->first << ' ' << it->second << "\n";
	}
	return 0;
}