#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int inf = 1e9 + 7;
const ll infll = 1e18;
template<typename T>
istream &operator>>(istream &is, vector<T> &a) {
for (auto &i : a) {
is >> i;
}
return is;
}
int32_t main() {
#ifdef LOCAL
freopen("/tmp/input.txt", "r", stdin);
#else
ios::sync_with_stdio(false);
cin.tie(nullptr);
#endif
int n;
cin >> n;
vector<pair<ll, int>> v(n);
for (auto &[a, b] : v) {
cin >> a >> b;
}
sort(v.begin(), v.end());
vector<ll> pref(n + 1);
for (int i = 1; i <= n; ++i) {
pref[i] = pref[i - 1] + v[i - 1].second;
}
ll mn = -infll;
ll ans = -infll;
for (int i = 0; i < n; ++i) {
mn = max(mn, -pref[i] + v[i].first);
ans = max(ans, pref[i + 1] - v[i].first + mn);
}
cout << ans << "\n";
return 0;
}
