#include "bits/stdc++.h"
#define int long long
using namespace std;

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
#ifdef LOCAL
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
    int n;
    cin >> n;
    vector<pair<int, int>> s(n);
    for (auto &[a, b] : s) {
        cin >> a >> b;
    }
    sort(s.begin(), s.end());
    vector<int> p(n + 1);
    for (int i = 1; i <= n; i++) {
        p[i] = p[i - 1] + s[i - 1].second;
    }

    set<int> Q;
    int ans = 0;
    for (int i = 0; i < n; i++) {
        Q.insert(-p[i] + s[i].first);
        ans = max(ans, p[i + 1] - s[i].first + *prev(Q.end()));
    }
    cout << ans << '\n';
    return 0;
}