#include <bits/stdc++.h>
using namespace std;
#define int long long
#define endl '\n'
class Solve {
public:
void solve() {
int n;
cin >> n;
vector<pair<int,int>> v(n + 1);
for (int i = 1; i <= n; i++) {
cin >> v[i].first >> v[i].second;
}
sort(v.begin() + 1, v.end());
vector<int> pref(n + 1, 0);
for (int i = 1; i <= n; i++) {
pref[i] = pref[i - 1] + v[i].second;
}
int ans = 0;
int tux = LLONG_MAX;
for (int r = 1; r <= n; r++) {
tux = min(tux, pref[r - 1] - v[r].first);
ans = max(ans, (pref[r] - v[r].first) - tux);
}
cout << ans << endl;
}
};
signed main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
Solve s;
s.solve();
}
