//Coded by Chirath Nirodha
#include<bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define PB push_back
#define MP make_pair
#define P push
#define I insert
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
const ll mod=1e9+7;
inline void io(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
}
void solve(){
int n;cin>>n;
vector<pair<ll,ll> > v;
for(int i=0;i<n;i++){
ll a,b;cin>>a>>b;
v.PB(MP(a,b));
}
sort(v.begin(),v.end());
ll cur=0,ans=0;
for(int i=0;i<n;i++){
ans=max(ans,cur+v[i].S-v[i].F);
ans=max(ans,v[i].S);
cur=max(cur+v[i].S,v[i].F+v[i].S);
}
cout<<ans<<endl;
}
int main(){
io();
solve();
//int t;cin>>t;for(int i=0;i<t;i++)solve();
return 0;
}
