#include<bits/stdc++.h>
#define mp make_pair
#define pb push_back
#define ii pair<int,int>
#define all(x) (x).begin(),(x).end()
#define INF 100000000000000000
#define modulo 1000000007
#define mod 998244353
#define int long long int
using namespace std;
int32_t main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
// freopen("q.gir","r",stdin);
// freopen("q.cik","w",stdout);
int n;
cin>>n;
vector<ii> arr(1,{-INF,-INF});
for(int i=0;i<n;i++){
int x,y;
cin>>x>>y;
arr.pb({x,y});
}
sort(all(arr));
vector<int>pre(n+1,0);
for(int i=1;i<=n;i++)pre[i]=pre[i-1]+arr[i].second;
int ans=-INF,mx=-INF;
for(int i=0;i<=n;i++){
ans=max(ans,pre[i]-arr[i].first+mx);
if(i+1<=n)
mx=max(mx,arr[i+1].first-pre[i]);
}
cout<<ans;
}
