#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
typedef long long int ll;
int N;
vector<pair<ll, ll>> artworks;
int main() {
ios::sync_with_stdio(false);
cin.tie(NULL);
cin >> N;
artworks = vector<pair<ll, ll>>(N);
for (int i = 0; i < N; i++)
cin >> artworks[i].first >> artworks[i].second;
sort(artworks.begin(), artworks.end());
for (int i = 1; i < N; i++)
artworks[i].second += artworks[i-1].second;
ll record = 0, cur;
for (int i = 0; i < N; i++) {
for (int j = i; j < N; j++) {
cur = artworks[j].second;
if (i > 0)
cur -= artworks[i-1].second;
cur += artworks[i].first;
cur -= artworks[j].first;
//cout << cur << '\n';
record = max(record, cur);
}
}
cout << record << '\n';
return 0;
}
