//#pragma GCC optimize("O3")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,tune=native")
//#pragma GCC optimize ("unroll-loops")
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
int n;
cin >> n;
vector<pair<ll, ll>> a(n);
for (auto& p : a) {
cin >> p.first >> p.second;
}
sort(a.begin(), a.end());
ll kek = a[0].first;
ll sum = a[0].second;
ll ans = sum;
for (int i = 1; i < n; i++) {
kek = max(kek, a[i].first - sum);
sum += a[i].second;
ans = max(ans, sum - a[i].first + kek);
}
cout << ans << endl;
return 0;
}
