#include<bits/stdc++.h>
#define int long long
using namespace std;
int n, mn[500001], mx[500001], ans;
pair<int, int> v[500001] = {};
signed main()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
cin >> n;
for (int i = 1; i <= n; i++)
cin >> v[i].first >> v[i].second;
sort(v, v + n + 1);
for (int i = 1; i <= n; i++)
v[i].second += v[i - 1].second;
mn[1] = v[0].second - v[1].first;
for (int i = 2; i <= n; i++)
mn[i] = min(mn[i - 1], v[i - 1].second - v[i].first);
mx[n] = v[n].second - v[n].first;
for (int i = n - 1; i >= 1; i--)
mx[i] = max(mx[i + 1], v[i].second - v[i].first);
for (int i = 1; i <= n; i++)
ans = max(ans, mx[i] - mn[i]);
cout << ans << '\n';
return 0;
}
