#include <iostream>
#include <algorithm>
using namespace std;
using ll=long long;
using pli=pair<ll,int>;
const int maxn = int(5e5) + 10;
const ll inf = 1ll<<60;
int n;
pli d[maxn];
int main()
{
cin.tie(0)->sync_with_stdio(0);
cin >> n;
for (int i=1; i<=n; ++i) cin >> d[i].first >> d[i].second;
sort(d+1, d+n+1);
ll cp=0, pm=-inf, ans=-inf;
for (int i=1; i<=n; ++i) {
cp += d[i].second;
ans = max(ans, cp + pm - d[i].first);
ans = max(ans, ll(d[i].second));
pm = max(pm, d[i].first - (cp - d[i].second));
}
cout << ans << '\n';
return 0;
}
