#include <bits/stdc++.h>
using namespace std;
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
int N;
cin >> N;
vector<pair<long long, int>> artworks(N);
for (int i = 0; i < N; i++) {
cin >> artworks[i].first >> artworks[i].second;
}
sort(artworks.begin(), artworks.end());
vector<long long> A(N + 1);
vector<int> B(N + 1);
for (int i = 1; i <= N; i++) {
A[i] = artworks[i - 1].first;
B[i] = artworks[i - 1].second;
}
vector<long long> pre(N + 1);
for (int i = 1; i <= N; i++) {
pre[i] = pre[i - 1] + B[i];
}
multiset<long long> ms;
for (int i = 1; i <= N; i++) {
ms.insert(pre[i] - A[i]);
}
long long ans = 0;
for (int i = 1; i <= N; i++) {
ans = max(ans, A[i] - pre[i - 1] + *ms.rbegin());
ms.erase(ms.find(pre[i] - A[i]));
}
cout << ans << '\n';
}
