#include<bits/stdc++.h>
using namespace std;
long long psm[500005];
int main(){
int n;
cin>>n;
vector<pair<long long,long long> >v;
long long mx2=-1*LLONG_MAX,mx=-1*LLONG_MAX;
for(int i=0;i<n;i++){
long long a,b;
cin>>a>>b;
v.push_back({a,b});
}
sort(v.begin(),v.end());
long long sum=0;
for(int i=0;i<n;i++){
sum+=v[i].second;
psm[i+1]=sum;
}
//cout<<endl;
for(int i=0;i<n;i++){
if(v[i].first-psm[i]>mx2){
mx2=v[i].first-psm[i];
}
//cout<<i<<" "<<psm[i+1]<<" "<<v[i].first<<" "<<mx2<<" ";
if(psm[i+1]-v[i].first+mx2>mx){
mx=psm[i+1]-v[i].first+mx2;
}
//cout<<mx<<"\n";
}
cout<<mx;
//3 1 1 20 2 21 30
}
