#include <bits/stdc++.h>
using namespace std;
#define int long long
bool sortt (const pair<int, int> &a, const pair <int, int> &b)
{
if (a.first!=b.first) return a.first<b.first;
else return a.second<b.second;
}
signed main()
{
ios::sync_with_stdio(false);
cin.tie(0);
int n; cin>>n;
vector <pair<int, int>> niz(n);
for (int i=0; i<n; i++) cin>>niz[i].first>>niz[i].second;
sort(niz.begin(), niz.end(), sortt);
/*cout<<"niz je: "<<endl;
for (int i=0; i<n; i++) cout<<niz[i].first<<" "<<niz[i].second<<endl;*/
vector <int> pref(n);
for (int i=0; i<n; i++) pref[i]=pref[i-1]*(i>0)+niz[i].second;
/*cout<<"pref je: "<<endl;
for (int i=0; i<n; i++) cout<<pref[i]<<" ";*/
cout<<endl;
int ans=0, minmin=-niz[0].first;
for (int i=1; i<n; i++)
{
ans=max(ans, pref[i]-niz[i].first-minmin);
minmin=min(minmin, pref[i-1]-niz[i].first);
}
cout<<ans<<endl;
return 0;
}
