#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
ll n, ans = 0; cin >> n;
vector<pair<ll, ll>> a(n + 1, {0, 0});
for (int i = 1; i <= n; i++) cin >> a[i].first >> a[i].second;
sort(a.begin(), a.end());
vector<ll> p(n + 1, 0), u(n + 1), v(n + 1), mxu(n + 1);
for (ll i = 1; i <= n; i++) p[i] = a[i].second + p[i - 1];
for (ll i = 1; i <= n; i++) u[i] = p[i] - a[i].first;
for (ll i = 1; i <= n; i++) v[i] = a[i].first - p[i - 1];
mxu[n] = u[n];
for (ll i = n - 1; i >= 1; i--) mxu[i] = max(mxu[i + 1], u[i]);
for (ll i = 1; i <= n; i++) ans = max(ans, mxu[i] + v[i]);
cout << ans;
}
