#include <bits/stdc++.h>
using namespace std;
int n;
pair<long long, long long> p[(int)5e5 + 10];
long long pref[(int) 5e5 + 10];
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
cin >> n;
for (int i = 1; i <= n; i++) {
cin >> p[i].first >> p[i].second;
}
sort(p + 1, p + n + 1);
for (int i = 1; i <= n; i++) {
pref[i] = pref[i - 1] + p[i].second;
}
long long ans = 0;
for (int l = 1; l <= n; l++) {
for (int r = l; r <= n; r++) {
ans = max(ans, pref[r] - pref[l - 1] - p[r].first + p[l].first);
}
}
cout << ans;
return 0;
}
