#include <bits/stdc++.h>
#define ll long long
using namespace std;
unordered_map<int, set<int, greater<int>>> m;
int n, x, y;
ll ans;
int main() {
	cin >> n;
	for (int i = 1; i <= n; i++) {
		cin >> x >> y;
		m[x].insert(y);
	}
	for (auto &i : m) {
		ans += *i.second.begin();
	}
	cout << ans;
	return 0;
}