#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
int n;
cin >> n;
vector<pair<ll,ll>> a(n);
for(int i=0;i<n;i++){
cin >> a[i].first >> a[i].second;
}
sort(a.begin(),a.end());
vector<ll> pref(n+1,0);
for(int i=0;i<n;i++){
pref[i+1] = pref[i]+a[i].second;
}
ll mn = LLONG_MAX;
//pref[r]-pref[l]-Ar+Al -> pref[r]-ar -pref[l]+al
ll best = LLONG_MIN;
for(int i=0;i<n;i++){
mn = min(pref[i]-a[i].first,mn);
best = max(best,pref[i+1]-a[i].first-mn);
}
cout << best;
}
