/*
* With a little appreciation, in a mostly hollow tone, she says, "Delightful." As if the world has any meaning.
* TASK : Art Exhibition
* AUTHOR : Marszpace
*/
#include<bits/stdc++.h>
using namespace std;
#define int long long
int32_t main(){
ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
int n;
cin >> n;
vector<pair<int,int>> arr(n);
for(int i=0;i<n;i++){
cin >> arr[i].first >> arr[i].second;
}
sort(arr.begin(),arr.end());
vector<int> qsum(n+1,0);
for(int i=0;i<n;i++){
qsum[i+1]=qsum[i]+arr[i].second;
}
int ans=-1,maxprev=-1e17;
for(int i=n;i>0;i--){
ans=max(ans,arr[i-1].second);
ans=max(ans,maxprev+arr[i-1].first-qsum[i-1]);
maxprev=max(maxprev,qsum[i]-arr[i-1].first);
}
cout << ans;
return 0;
}
