#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
// pref[j + 1] - pref[i] - (a[j] - a[i])
// pref[j + 1] - a[j] - pref[i] + a[i]
int main() {
ios_base::sync_with_stdio(false); cin.tie(0); cout.setf(ios::fixed); cout.precision(20);
#ifdef LOCAL
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#endif
int n;
cin >> n;
vector <ll> a(n), b(n);
for (int i = 0; i < n; ++i) {
cin >> a[i] >> b[i];
}
vector <int> idx(n);
iota(idx.begin(), idx.end(), 0);
sort(idx.begin(), idx.end(), [&] (int i, int j) {
return a[i] < a[j];
});
vector <ll> pref(n + 1);
for (int i = 0; i < n; ++i) {
pref[i + 1] = pref[i] + b[idx[i]];
}
ll ans = 0;
ll mx = -2e18;
for (int i = 0; i < n; ++i) {
mx = max(mx, a[idx[i]] - pref[i]);
ans = max(ans, mx + pref[i + 1] - a[idx[i]]);
}
cout << ans << '\n';
}
