#include? < stdio.h >
#include? < stdlib.h >

#define ?N?50001

struct ?Node
{
???? int ?a,?b;
} ;

Node?d[N];
int ??n;

int ?cmp(? const ? void * ?a,? const ? void * ?b?)
{
????Node * ?ta = ?(Node * )a;
????Node * ?tb = ?(Node * )b;
????
???? if (?ta -> a == ?tb -> a?)? return ?ta -> b - ?tb -> b;
????
???? return ?ta -> a - ?tb -> a;
}

int ?main()
{
????scanf( " %d " ,? & n);
????
???? for (? int ?i = ? 0 ;?i < ?n;? ++ i?)??scanf( " %d%d " ,? & d[i].a,? & d[i].b?);
????qsort(?d,?n,? sizeof (?d[ 0 ]?),?cmp?);
????
???? int ?min = ?d[ 0 ].a,?max = ?d[ 0 ].b;
???? for (? int ?i = ? 1 ;?i < ?n;? ++ i?)
???? {
???????? if (?d[i].a > ?max?)
???????? {
????????????printf( " %d?%d\n " ,?min,?max?);
????????????min = ?d[i].a,?max = ?d[i].b;
????????}
???????? else ? if (?d[i].b > ?max?)?max = ?d[i].b;
????}
????printf( " %d?%d\n " ,?min,?max?);
????
???? return ? 0 ;
}