#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int main(){
ios_base::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
int nums; cin >> nums;
vector<pair<ll, ll>> vec(nums + 1);
for (int i = 1; i <= nums; i++){
ll s, v; cin >> s >> v;
vec[i] = {s, v};
}
sort(vec.begin() + 1, vec.end());
vector<ll> pref(nums + 1);
multiset<ll> s;
pref[0] = 0;
for (int i = 1; i <= nums; i++){
pref[i] = pref[i - 1] + vec[i].second;
s.insert(pref[i] - vec[i].first);
}
ll ans = 0;
for (int i = 1; i <= nums; i++){
ans = max(ans, *s.rbegin() - pref[i - 1] + vec[i].first);
s.erase(s.find(pref[i] - vec[i].first));
}
cout << ans;
}
