#include<iostream>
#include<algorithm>
using namespace std;
int main(){
	cin.tie(0);
	ios::sync_with_stdio(0);
	long long broiMonitori,broqch,koiPored=0,broqch1;
	bool imaLiTakuv=false;
	cin>>broiMonitori;
	long long sbor[broiMonitori],viso4ina[broiMonitori],dulzina[broiMonitori],koiSaViso4init[broiMonitori];
	for(broqch=0;broqch<broiMonitori;broqch++){
		imaLiTakuv=false;
		cin>>dulzina[broqch]>>viso4ina[broqch];
		for(broqch1=koiPored-1;broqch1>=0 and imaLiTakuv==false;broqch1--){
			if(viso4ina[broqch]==koiSaViso4init[broqch1]){
				imaLiTakuv=true;
				sbor[broqch1]=dulzina[broqch]+sbor[broqch1];
			}
		}
		if(imaLiTakuv==false){
			sbor[koiPored]=dulzina[broqch];
			koiSaViso4init[koiPored]=viso4ina[broqch];
			koiPored++;
		}
	}
	sort(sbor,sbor+koiPored);
	cout<<sbor[koiPored-1]<<"\n";
	cout<<"\n";
	return 0;
}

