#include <bits/stdc++.h>
using namespace std;
#define all(x) x.begin(), x.end()
#define siz(x) int(x.size())
#define ll long long
#define ar array
#define vt vector
#define inf INT_MAX
#define lnf LLONG_MAX
const int nxm = int(5e5) + 7;
int n;
pair<ll, ll> a[nxm];
namespace sub3 {
void solve() {
sort(a, a + n);
for (int i = 1; i < n; ++i) {
a[i].second += a[i - 1].second;
}
ll ans = -lnf;
for (int i = 0; i < n; ++i) {
for (int j = i; j < n; ++j) {
ans = max(ans, a[j].second - (i - 1 >= 0 ? a[i - 1].second : 0) - a[j].first + a[i].first);
}
}
cout << ans << "\n";
}
};
namespace sub4 {
void solve() {
sort(a, a + n);
for (int i = 1; i < n; ++i) {
a[i].second += a[i - 1].second;
}
ll ans = -lnf;
ll prf = -lnf;
for (int i = 0; i < n; ++i) {
prf = max(prf, a[i].first - (i - 1 >= 0 ? a[i - 1].second : 0));
ans = max(ans, a[i].second - a[i].first + prf);
}
cout << ans << "\n";
}
};
int subtask() {
if (n <= 5000) {
return 3;
}
return 4;
};
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> n;
for (int i = 0; i < n; ++i) {
cin >> a[i].first >> a[i].second;
}
if (subtask() == 3) {
sub3::solve();
} else {
sub4::solve();
}
return 0;
}
