#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll INF = 1e18;
signed main() {
cin.tie(0); ios::sync_with_stdio(false);
ll N;
cin >> N;
vector<pair<ll,ll>> v(N);
for(ll i = 0; i < N; i++) {
cin >> v[i].first >> v[i].second;
}
sort(v.begin(), v.end());
for(ll i = 0; i < N; i++) {
if (i) v[i].second += v[i-1].second;
}
ll pref = v[0].first;
ll res = -v[0].first + v[0].second + pref;
for(ll i = 1; i < N; i++) {
pref = max(pref, v[i].first - v[i-1].second);
res = max(res, -v[i].first + v[i].second + pref);
}
cout << res;
}
