#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define vll vector<ll>
#define vbool vector<bool>
#define pairll pair<ll, ll>
#define pb push_back
#define fi first
#define sc second
const ll md = 1e9+7;
void solve(){
ll n; cin >> n;
vector<pairll> a(n+1); for(ll i = 1; i <= n; i++) cin >> a[i].fi >> a[i].sc;
sort(a.begin(), a.end());
a[0].fi = a[1].fi;
vll p(n+1), pf(n+1);
multiset<ll, greater<ll>> ms;
for(ll i = 1; i <= n; i++){
p[i] = a[i].sc - (a[i].fi - a[i-1].fi);
pf[i] = pf[i-1] + p[i];
ms.insert(pf[i]);
// cout << pf[i] << ' ';
}//cout << endl;
ll res = 0;
ll tot = 0;
for(ll i = 1; i <= n; i++){
res = max(res, tot + *ms.begin());
tot += a[i+1].fi - a[i].fi;
tot -= a[i].sc;
ms.erase(ms.find(pf[i]));
}cout << res << endl;
}
int main(){
ll t = 1; //cin >> t;
while(t--)solve();
}
