#include <bits/stdc++.h>
using namespace std;
 
bool cmp(const pair<int, int>& a, const pair<int, int>& b) {
	if(a.first != b.first)
		return a.first < b.first;
 
	return a.second > b.second;
}
 
int main() {
	ios_base::sync_with_stdio(false), cin.tie(0);
 
	int n, a, b;
	set<pair<int, int>, decltype(cmp)*> S(cmp);
 
	cin >> n;
	while(n--) {
		cin >> a >> b;
 
		S.insert({b, a});
	}
 
	int ans = 0;
 
	while(!S.empty()) {
		auto it = S.begin();
 
		while(it != S.end()) {
			cout << it -> first << ' ' << it -> second << '\n';
 
			auto nxtIt = S.lower_bound({it -> first + 1, it -> second});
 
			S.erase(it);
			it = nxtIt;
		}
 
		ans++;
	}
 
	cout << ans;
}

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5
172 1
161 2
188 4
154 2
180 1