#include<bits/stdc++.h>
using namespace std;
int n;const int maxx=5e4+5;
pair<int,int> q[maxx];
vector<pair<int,int> > ans;
bool cmp(pair<int,int> a,pair<int,int> b)
{return a.first<b.first;}
int main()
{
	cin>>n;
	for(int i=1;i<=n;i++) cin>>q[i].first>>q[i].second;
	sort(q+1,q+n+1,cmp);
	int i=1,cnt=0;
	while(i<=n)
	{
		int head=q[i].first,tail=q[i].second;
		for(;;i++)
		{
			if(q[i].first>tail) {i--;break;}
			if(q[i].second>tail) tail=q[i].second;
		}
		ans.push_back(make_pair(head,tail));i++;cnt++;
	}
	for(int k=0;k<=cnt-1;k++) cout<<ans[k].first<<" "<<ans[k].second<<endl;
	return 0;
}

segmentation fault with invalid memory reference