#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 + 1);
for (ll i = 1; i<=n; ++i)
cin >> pics[i].first >> pics[i].second;
sort(pics.begin(), pics.end());
vector<ll> pref(n, 0);
for (int i = 1; i<=n; ++i)
pref[i] = pref[i - 1] + pics[i].second;
ll val = 0;
ll res = 0;
for (int i = 1; i<=n; ++i) {
val = max(val, pics[i].first - pref[i - 1]);
res = max(res, pref[i] - pics[i].first + val);
}
cout << res << '\n';
}
