#include<bits/stdc++.h>
using namespace std;
using ll=long long;
inline void solve(){
int n; cin>>n;
ll suf=0,mx=0;
vector<pair<ll, ll>> a(n);
multiset<ll> m;
for(int i=0;i<n;++i) cin>>a[i].first>>a[i].second;
sort(a.begin(),a.end());
for(int i=n-1;i>=0;--i){
suf+=a[i].first+a[i].second;
m.insert(suf);
suf-=a[i].first;
}
suf=0;
for(int i=n-1;i>=0;--i){
mx=max(mx,*m.rbegin()-a[i].first-suf);
suf+=a[i].second;
m.erase(m.find(a[i].first+suf));
}
cout<<mx;
}
int main(){
ios::sync_with_stdio(false); cin.tie(nullptr);
int t=1;
for(int i=0;i<t;++i){
solve();
}
}
