#include <iostream>
#include <vector>
#include <unordered_map>
#include <algorithm>
typedef long long ll;
using namespace std;
int main() {
ll n;
cin >> n;
vector<pair<ll, ll>> pics(n);
// {size, val}
ll t = 0;
for (ll i = 0; i<n; ++i) {
cin >> pics[i].first >> pics[i].second;
t = max(t, pics[i].second);
}
sort(pics.rbegin(), pics.rend());
ll res = 0;
for (ll i = 0; i<n; ++i) {
ll curr = pics[i].first * -1;
ll sum = pics[i].second;
for (ll j = i + 1; j<n; ++j) {
sum += pics[j].second;
res = max(res, curr + sum + pics[j].first);
}
}
cout << max(res, t) << '\n';
}
