#include <bits/stdc++.h>
#define pii pair<int,int>
#define pll pair<ll,ll>
#define ll long long
using namespace std;
const int MAX=5e5+5;
const ll INF=1LL<<60;
int N;
pll P[MAX];
ll A[MAX],B[MAX];
ll pre[MAX];
int main(){
ios::sync_with_stdio(0);cin.tie(0);
cin>>N;
for (int i=0;i<N;i++) cin>>P[i].first>>P[i].second;
sort(P,P+N);
for (int i=0;i<N;i++) A[i]=P[i].first,B[i]=P[i].second;
ll p=0;
for (int i=0;i<N;i++) pre[i]=p,p+=B[i];
pre[N]=p;
ll m=-INF;
ll ans=-INF;
for (int i=0;i<N;i++){
m=max(m,-pre[i]+A[i]);
ans=max(ans,pre[i+1]-A[i]+m);
}
cout<<ans<<'\n';
}
