#include <bits/stdc++.h>
using namespace std;
#define f first
#define s second
#define ll long long
int main() {
ios_base::sync_with_stdio(false); cin.tie(NULL);
int n;
cin >> n;
vector<pair<ll,ll>> a(n);
for (auto& [A,B] : a)
cin >> A >> B;
sort(a.begin(), a.end());
vector<ll> qs(n);
qs[0] = a[0].s;
for (int i = 1; i < n; i++)
qs[i] = qs[i-1]+a[i].s;
ll ans=0;
for (int i = 0; i < n; i++)
for (int j = i+1; j < n; j++)
ans = max(ans, qs[j]-(i > 0 ? qs[i-1] : 0)-a[j].f+a[i].f);
cout << ans;
return 0;
}
