#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define int long long
#define endl '\n'
using namespace std;
using namespace __gnu_pbds;
using ordered_set = tree<int,null_type,less_equal<int>,rb_tree_tag,tree_order_statistics_node_update>;
signed main(){
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
int n;
cin>>n;
pair<int,int>pr[n];
for(auto &i:pr)cin>>i.first>>i.second;
sort(pr,pr+n);
int ans=0,sm=0;
for(int i=n-1;i>=0;i--){
ans=max(ans,sm+pr[i].second);
if(i)sm=max(0ll,sm+pr[i].second-pr[i].first+pr[i-1].first);
}
cout<<ans;
}
