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