#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#define ordered_set <int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update>
#define ordered_multiset <int, null_type, less_equal <int>, rb_tree_tag, tree_order_statistics_node_update>
#define int long long
#define double long double
#define pii pair <int, int>
#define tiii tuple <int, int, int>
#define tiiii tuple <int, int, int, int>
#define emb emplace_back
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define iShowSpeed cin.tie(NULL)->sync_with_stdio(false)
#define matrix vector <vector <int>>
#define mat(n, m) vector <vector <int>> (n, vector <int> (m));
const int mod = 1e9 + 7;
const int inf = 1e18;
const matrix II = {{1, 0}, {0, 1}};
void solve(){
int n; cin >> n;
vector <pii> a(n + 1); for (int i = 1; i <= n; i++) cin >> a[i].first >> a[i].second;
sort(all(a));
vector <int> pref(n + 1); for (int i = 1; i <= n; i++) pref[i] = pref[i - 1] + a[i].second;
int mx = pref[n] - a[n].first;
int ans = a[n].second;
for (int i = n - 1; i >= 1; i--) ans = max(ans, a[i].second), ans = max(ans, a[i].first - pref[i - 1] + mx), mx = max(mx, pref[i] - a[i].first);
cout << ans;
}
int32_t main(){
iShowSpeed;
// int q; cin >> q; while (q--)
solve();
}
/*
for an index i -> ans = max(pref[j] - pref[i - 1] - (a[j] - a[i]))
= a[i] - pref[i - 1] + max(pref[j] - a[j]);
*/
