#include<iostream>
using namespace std;
int main(){
long long broimonitori,index,naigolqmo=0,segashno=0,index2=0,segashno2=0,broyach=0,naigolqmo2=0;
cin>>broimonitori;
long long duljina[broimonitori],shirina[broimonitori];
long long pazitel[broimonitori];
for(index=0;index<broimonitori;index++){
cin>>duljina[index]>>shirina[index];
pazitel[index]=0;	
}
for(index=0;index<broimonitori;index++){
	segashno=shirina[index];
	segashno2=duljina[index];
 for(index2=index+1;index2<broimonitori;index2++){
 if(naigolqmo<segashno2){
 naigolqmo=segashno2;	
 }
 if(segashno==shirina[index2]){
 naigolqmo+=duljina[index2];	
 }
 }
 pazitel[broyach]=naigolqmo;
 broyach++;
 naigolqmo=0;
}
naigolqmo2=pazitel[0];
for(index=0;index<broyach;index++){
if(naigolqmo2<pazitel[index]){
naigolqmo2=pazitel[index];	
}
}
cout<<naigolqmo2;
return 0;
}
