#include <bits/stdc++.h>
#define ll long long
using namespace std;
int main() {
ios_base::sync_with_stdio(0);
cin.tie(nullptr);
int n;
cin >> n;
vector<pair<ll, ll>> v(n + 1);
for (int i = 1; i <= n; i++) {
cin >> v[i].first >> v[i].second;
}
sort(v.begin() + 1, v.end());
vector<ll> a(n + 1), b(n + 1, 0);
for (int i = 1; i <= n; i++) {
a[i] = v[i].first;
b[i] = b[i - 1] + v[i].second;
}
ll mn = 1e18, ans = 0;
for (int i = 1; i <= n; i++) {
mn = min(mn, b[i - 1] - a[i]);
ans = max(ans, b[i] - a[i] - mn);
}
cout << ans;
}
