#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define read freopen("in.txt","r",stdin);freopen("out.txt","w",stdout);
#define LESSGO ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
const ll N=1e6+10,M=505,OO=1e16,mod=1e9+7;
int n;
ll ans,pref[N],v[N];
pair<ll,ll>a[N];
int main(){
cin>>n;
for(int i=0;i<n;++i){
cin>>a[i].first>>a[i].second;
}
sort(a,a+n);
pref[0]=a[0].second;
for(int i=1;i<n;++i){
pref[i]=pref[i-1]+a[i].second;
}
set<ll>s;
for(int i=0;i<n;++i){
s.insert(pref[i]-a[i].first);
v[i]=pref[i]-a[i].first;
}
for(int i=0;i<n;++i){
ll cur=(i?pref[i-1]:0)-a[i].first;
if(s.empty()) continue;
auto it=--(s.end());
cur=*it-cur;
ans=max(ans,cur);
auto f=s.find(pref[i]-a[i].first);
if(f==s.end()) continue;
s.erase(f);
}
cout<<ans<<'\n';
}
