#include <bits/stdc++.h>
using namespace std;
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int64_t n, a, b;
vector<pair<int64_t, int64_t>> obrazy;
cin >> n;
int64_t sumy[n + 1] = {0}, pref[n + 1];
for(int i = 0; i < n; i++){
cin >> a >> b;
obrazy.push_back({a, b});
}
//cout << endl;
sort(obrazy.begin(), obrazy.end());
pref[0] = obrazy[0].first;
for(int i = 0; i < n; i++){
a = obrazy[i].first;
b = obrazy[i].second;
sumy[i + 1] = sumy[i] + b;
pref[i + 1] = max(pref[i], a - sumy[i]);
//cout << sumy[i + 1] << " " << pref[i + 1] << " " << a << endl;
}
int64_t wyn = 0;
//cout << endl;
for(int i = 0; i < n; i++){
wyn = max(wyn, sumy[i + 1] + pref[i + 1] - obrazy[i].first);
//cout << sumy[i + 1] << " " << pref[i + 1] << " " << obrazy[i].first << endl;
}
cout << wyn;
}
