#include<bits/stdc++.h>
using namespace std;
using ll=long long;
using ull=unsigned long long;
#define rep(i,a,b) for(int i=(a); i<(b); ++i)
#define all(array) array.begin(), array.end()
#define bitcnt(x) ((sizeof(x) <= sizeof(int)) ? (32 - __builtin_clz(x)) : (64 - __builtin_clzll(x)))
//#define OJ
#ifndef OJ
#define debug(x) cerr<<"line "<<__LINE__<<": "<<#x<<" "; _print(x); cerr<<'\n';
#else
#define debug(x)
#endif
template<class T> void _print(T a);
template<class T, class V> void _print(pair<T, V> &p);
template<class T> void _print(vector<T> &a);
template<class T> void _print(set<T> &s);
template<class T, class V> void _print(map<T, V> &mp);
template<class T> void _print(deque<T> &d);
template<class T> void _print(stack<T> st);
template<class T> void _print(queue<T> q);
template<class T> void _print(priority_queue<T> pq);
template<class T> void _print(T a){cerr<<a;}
template<class T, class V> void _print(pair<T, V> &p){cerr<<"{"; _print(p.first); cerr<<", "; _print(p.second); cerr<<"}";}
template<class T> void _print(vector<T> &a){cerr<<"[ "; for(auto c:a){_print(c);cerr<<" ";} cerr<<"]";}
template<class T> void _print(set<T> &s){cerr<<"[ "; for(auto c:s){_print(c);cerr<<" ";} cerr<<"]";}
template<class T, class V> void _print(map<T, V> &mp){cerr<<"[ ";for(auto c:mp){_print(c); cerr<<" ";} cerr<<"]";}
template<class T> void _print(deque<T> &d){cerr<<"[ "; for(auto c:d){_print(c); cerr<<" ";} cerr<<"]";}
template<class T> void _print(stack<T> st){cerr<<"| "; while(!st.empty()){auto c=st.top(); st.pop(); _print(c); cerr<<" ";} cerr<<"|";}
template<class T> void _print(queue<T> q){cerr<<"( "; while(!q.empty()){auto c=q.front(); q.pop(); _print(c); cerr<<" ";} cerr<<")";}
template<class T> void _print(priority_queue<T> pq){cerr<<"< ";while(!pq.empty()){auto c=pq.top(); pq.pop(); _print(c); cerr<<" ";} cerr<<">";}
//===============================================================MAIN CODE=============================================================================================
inline void solve(){
int n; cin>>n;
ll suf=0,mx=0;
vector<pair<ll, ll>> a(n);
multiset<ll> m;
rep(i,0,n) cin>>a[i].first>>a[i].second;
sort(all(a));
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){
//cout<<"Case "<<i+1<<": "<<'\n';
solve();
}
}
