#include <bits/stdc++.h>
using namespace std;
int main() {
long long n;
cin >> n;
vector<pair<long long, long long>> art(n+1);
for (long long i = 1; i <= n; i++) {
cin >> art[i].first >> art[i].second;
}
sort(art.begin(), art.end()); // sort on the size of the arts
vector<long long> pref_val(n+1, 0);
vector<long long> size(n+1);
for (long long i = 1; i <= n; i++) {
size[i] = art[i].first;
pref_val[i] = pref_val[i-1] + art[i].second;
}
long long ans = LLONG_MIN;
long long minn = LLONG_MAX;
for (long long i = 1; i <= n; i++) {
minn = min(minn, pref_val[i-1] - size[i]);
ans = max(ans, pref_val[i] - size[i] - minn);
}
cout << ans << endl;
}
