#include <bits/stdc++.h>
using namespace std;
#define int long long
int32_t main() {
int n; cin >> n;
vector<pair<int,int>> arts(n);
for (int i=0;i<n;i++) {
cin >> arts[i].first >> arts[i].second;
}
sort(arts.begin(), arts.end());
int ans = arts[0].second, leftsum = arts[0].second;
vector<int> diffvec = {0};
priority_queue<int> diffs; diffs.push(0);
for (int i=1;i<n;i++) {
diffvec.push_back(diffvec.back() + arts[i].first - arts[i-1].first - arts[i-1].second);
diffs.push(diffvec.back());
leftsum += arts[i].second - (arts[i].first - arts[i-1].first);
//cout << ans << ' ' << diffs.top() << '\n';
ans = max(ans, leftsum + diffs.top());
}
cout << ans;
}
