#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define mp make_pair
#define f first
#define s second
#define ll long long
#define ld long double
#define all(_v) _v.begin(), _v.end()
#define sz(_v) (int)_v.size()
#define pii pair <int, int>
#define pll pair <ll, ll>
#define veci vector <int>
#define vecll vector <ll>
const int dx[4] = {1, -1, 0, 0};
const int dy[4] = {0, 0, -1, 1};
const double PI = 3.1415926535897932384626433832795;
const double eps = 1e-9;
const int MOD1 = 1e9 + 7;
const int MOD2 = 998244353;
const int MAXN = 5e5 + 10;
int n;
pll a[MAXN];
int ord[MAXN];
ll pref[MAXN];
void solve() {
cin >> n;
for(int i = 1; i <= n; ++i)
cin >> a[i].f >> a[i].s;
sort(a + 1, a + n + 1);
for(int i = 1; i <= n; ++i)
pref[i] = pref[i - 1] + a[i].s;
ll ans = a[1].s, res = -a[1].f;
for(int i = 2; i <= n; ++i) {
ans = max(ans, max(a[i].s, pref[i] - a[i].f - res));
res = min(res, pref[i - 1] - a[i].f);
}
if(n <= 5000) {
for(int i = 1; i <= n; ++i)
for(int j = i; j <= n; ++j) ans = max(ans, pref[j] - a[j].f - (pref[i - 1] - a[i].f));
}
cout << ans;
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int CNT_TESTS = 1;
///cin >> CNT_TESTS;
for(int NUMCASE = 1; NUMCASE <= CNT_TESTS; ++NUMCASE) {
solve();
if(NUMCASE != CNT_TESTS) cout << '\n';
}
return 0;
}
