#include <iostream>
#include <vector>
#include <utility>
using namespace std;
int main()
{
	int n;
	vector<pair<long long,long long> > heigths;
	cin >> n;
	for(int i = 0;i < n;i ++)
	{
		long long sizeX, sizeY;
		cin >> sizeX >> sizeY;
		pair<long long,long long> pusher;
		pusher.first = sizeX;
		pusher.second = sizeY;
		bool finded = false;
		for(long long o = 0;o < heigths.size();o ++)
		{
			if(sizeY == heigths[o].first)
			{
				finded = true;
				heigths[o].second += sizeX;
			}
		}
		if(finded == false)
		{
			pair<long long,long long> pusher;
			pusher.first = sizeY;
			pusher.second = sizeX;
			heigths.push_back(pusher);
		}
	}
	long long max = 0;
	for(long long i = 0;i < heigths.size();i ++)
	{
		if(heigths[i].second > max)
		{
			max = heigths[i].second;
		}
	}
	cout << max << endl;
	return 0;
}
