#include<bits/stdc++.h>
using namespace std;
using ll = long long;
const int N = 5e5 + 5;
const ll inf = 1e18;
#define fi first
#define se second
int n;
pair<ll, ll> p[N];
ll f[N], s[N];
ll ans = -inf;
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> n;
for (int i = 1; i <= n; i++) cin >> p[i].fi >> p[i].se;
sort(p + 1, p + 1 + n);
for (int i = 1; i <= n; i++) f[i] = f[i - 1] + p[i].se;
s[n + 1] = -inf;
for (int i = n; i >= 1; i--) s[i] = max(s[i + 1], f[i] - p[i].fi);
for (int i = 1; i <= n; i++) {
ans = max(ans, p[i].fi + s[i] - f[i - 1]);
}
cout << ans;
return 0;
}
