#include <bits/stdc++.h>
using namespace std;
#define int long long
typedef pair<int, int> ii;
signed main() {
int n = 0;
cin >> n;
vector<ii> art(n, ii(0, 0));
for (int i = 0; i < n; ++i) {
cin >> art[i].first >> art[i].second;
}
sort(art.begin(), art.end());
vector<int> preval(n, 0);
preval[0] = art[0].second;
for (int i = 1; i < n; ++i) {
preval[i] = preval[i - 1] + art[i].second;
}
vector<int> pxax(n, 0);
for (int i = 0; i < n; ++i) {
pxax[i] = preval[i] - art[i].first;
}
int maxval = 0, minpiai = LLONG_MAX;
for (int i = 0; i < n; ++i) {
int v = i > 0 ? preval[i-1] : 0;
int piai = v - art[i].first;
minpiai = min(minpiai, piai);
maxval = max(maxval, pxax[i] - minpiai);
}
cout << maxval << '\n';
return 0;
}
