#include <bits/stdc++.h>
using namespace std;
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int n;
cin >> n;
vector<pair<int64_t, int>> v(n);
for (int i = 0; i < n; i++) {
cin >> v[i].first >> v[i].second;
}
sort(v.begin(), v.end());
vector<int64_t> a(n);
vector<int> b(n);
for (int i = 0; i < n; i++) {
a[i] = v[i].first;
b[i] = v[i].second;
}
int64_t mn = 1e18, sum = 0, ans = 0;
for (int i = 0; i < n; i++) {
sum += b[i];
mn = min(mn, sum - a[i] - b[i]);
ans = max(ans, sum - a[i] - mn);
}
cout << ans << '\n';
return 0;
}
