#include<bits/stdc++.h>
using namespace std;
int n;
struct node{
int b,e;
}a[1000010];
bool cmp(node x,node y){
return x.b<y.b;//按左端点排序
}
int main(){
cin>>n;
for(int i=1;i<=n;i++){
cin>>a[i].b>>a[i].e;
}
sort(a+1,a+1+n,cmp);
int l=a[1].b,r=a[1].e;
for(int i=2;i<=n;i++){
if(a[i].b<=r) r=max(r,a[i].e);//如果a[i]的左端点<r,就合并区间
else{//否则为独立区间,输出左端点与右端点
cout<<l<<" "<<r<<"\n";
l=a[i].b,r=a[i].e;
}
}
cout<<l<<" "<<r<<"\n";
return 0;
}