//#pragma GCC optimize("O3")
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define pb push_back
#define ff first
#define ss second
#define MOD 1000000009
#define INF 1000000019
#define INFL 1000000000000000099LL
#define MX 507
ll n,q,s,t,a,b,c,d,ans,bst,k,e,m,pier,h,w;
vector<pair<ll,ll>>v;
vector<ll>pref,pref2;
int main()
{
ios_base::sync_with_stdio(0);cin.tie(0);
cin>>n;
for(ll i=0;i<n;i++){
cin>>a>>b;
v.pb({a,b});
}
sort(v.begin(),v.end());
pref.pb(v[0].ss);
pref2.pb(v[0].ss+v[0].ff-v[1].ff);
for(ll i=1;i<n;i++){
pref.pb(pref.back()-v[i].ff+v[i].ss+v[i-1].ff);
// cout<<v[i].ff<<" "<<v[i].ss<<"\n";
// cout<<pref.back()<<"\n";
if(i+1<n)
pref2.pb(pref.back()+v[i].ff-v[i+1].ff);
// cout<<pref2.back()<<" ";
}
for(ll i=0;i<n;i++){
ans=max(ans,pref[i]-bst);
if(i+1!=n)
bst=min(bst,pref2[i]);
}
cout<<ans;
}
