#include <bits/stdc++.h>
#define fi first
#define se second
using namespace std;
long long n,suf[500005],pmax[500005],ans;
pair<long long, long long > arr[500005];
bool cmp(pair<long long, long long > a, pair<long long, long long > b){
return a.fi>b.fi;
}
int main(){
cin>>n;
for(int i =1;i<=n;i++)cin>>arr[i].fi>>arr[i].se;
sort(arr+1,arr+n+1,cmp);
for(int i =n;i>=1;i--){
suf[i]=suf[i+1]+arr[i].se;
}
pmax[0]=-1e18;
for(int i =1;i<=n;i++){
pmax[i] = max(pmax[i-1],suf[i]-arr[i].fi);
}
for(int i =n;i>=1;i--){
ans = max(ans,arr[i].se);
ans = max(ans,pmax[i-1]+arr[i].fi-suf[i+1]);
}
cout<<ans<<endl;
}
