#include <bits/stdc++.h>
#define int long long
#define IO ios::sync_with_stdio(0), cin.tie(0)
#define FOR(i, a, b) for (int i = a; i <= b; i++)
using namespace std;
using pii = pair<int, int>;
void dbg() {;}
template<class T, class ...U>
void dbg(T a, U ...b) { cout << a << " "; dbg(b...); }
void ent() { cout << "\n"; }
const int INF = 1e17;
const int N = 500005;
pii a[N];
int pre[N];
int bef[N], bck[N];
signed main() {
IO;
int n;
cin >> n;
FOR(i, 1, n) cin >> a[i].first >> a[i].second;
sort(a + 1, a + n + 1, [&](pii p, pii q) {
return p.first < q.first;
});
FOR(i, 1, n)
pre[i] = pre[i - 1] + a[i].second;
bef[0] = -INF;
for (int i = 1; i <= n; i++) {
bef[i] = a[i].first - pre[i - 1];
bef[i] = max(bef[i], bef[i - 1]);
}
bck[n + 1] = -INF;
for (int i = n; i >= 1; i--) {
bck[i] = pre[i] - a[i].first;
bck[i] = max(bck[i], bck[i + 1]);
}
int ans = -INF;
for (int i = 1; i <= n; i++)
ans = max(ans, bef[i] + bck[i]);
cout << ans << "\n";
return 0;
}
